diff --git a/SF50 Shared/Defaults.swift b/SF50 Shared/Defaults.swift
index a0510d3..b5f4d83 100644
--- a/SF50 Shared/Defaults.swift	
+++ b/SF50 Shared/Defaults.swift	
@@ -230,6 +230,18 @@ extension Operation {
       case .landing: Defaults[.landingRunway]
     }
   }
+
+  /// Forgets the airport and the runway selected for this leg.
+  public func clearSelection() {
+    switch self {
+      case .takeoff:
+        Defaults[.takeoffAirport] = nil
+        Defaults[.takeoffRunway] = nil
+      case .landing:
+        Defaults[.landingAirport] = nil
+        Defaults[.landingRunway] = nil
+    }
+  }
 }
 
 // MARK: - Measurement
diff --git a/SF50 TOLD/Loaders/NavDataLoader/NavDataLoaderViewModel.swift b/SF50 TOLD/Loaders/NavDataLoader/NavDataLoaderViewModel.swift
index 4d7b8c9..c3ee05d 100644
--- a/SF50 TOLD/Loaders/NavDataLoader/NavDataLoaderViewModel.swift	
+++ b/SF50 TOLD/Loaders/NavDataLoader/NavDataLoaderViewModel.swift	
@@ -350,10 +350,51 @@ final class NavDataLoaderViewModel: WithIdentifiableError {
   private func install(generation: Int) throws {
     try installer.install(generation: generation)
     clearNOTAMs()
+    clearSelectionsMissing(fromGeneration: generation)
     // The app watches the active generation and reopens its own store; doing it here as well would
     // race that, and leave the container the views hold pointing at the older file.
   }
 
+  /// Forgets a selected airport the incoming dataset no longer carries, and the runway chosen on
+  /// it.
+  ///
+  /// The FAA retires airports between cycles, and occasionally corrects the site number that
+  /// identifies one, so a selection made under an earlier dataset can name a record the new one
+  /// does not hold. Left in place it resolves to nothing in the widget and in Siri, which report a
+  /// missing airport and suggest reloading the very data that removed it.
+  ///
+  /// Internal so a test can run the check against a generation on disk without downloading one.
+  func clearSelectionsMissing(fromGeneration generation: Int) {
+    guard let context = try? navDataContext(forGeneration: generation) else { return }
+    for operation in Operation.allCases {
+      guard let recordID = operation.selectedAirportRecordID,
+        airportIsMissing(recordID, from: context)
+      else { continue }
+      operation.clearSelection()
+      logger.notice(
+        "Cleared the \(operation.rawValue, privacy: .public) airport, absent from the new dataset"
+      )
+    }
+  }
+
+  /// Whether the dataset lacks the airport a selection names. A failed fetch reads as present, so
+  /// nothing is cleared on the strength of an error.
+  private func airportIsMissing(_ recordID: String, from context: ModelContext) -> Bool {
+    do { return try findAirport(for: recordID, in: context) == nil } catch { return false }
+  }
+
+  /// A context on the generation just installed.
+  ///
+  /// The container the views hold still reads the previous generation here, so this check opens the
+  /// new one itself. In-memory stores cannot be shared between containers, so tests and previews
+  /// read the container they were given.
+  private func navDataContext(forGeneration generation: Int) throws -> ModelContext {
+    guard !container.configurations.contains(where: \.isStoredInMemoryOnly) else {
+      return ModelContext(container)
+    }
+    return ModelContext(try AppStore.makeContainer(layout: .appGroup, generation: generation))
+  }
+
   /// Discards the NOTAMs the pilot entered against the dataset just replaced.
   ///
   /// A NOTAM carries no effective time, so one written against a previous cycle would otherwise
diff --git a/SF50 TOLD/Views/Pickers/RunwayPicker.swift b/SF50 TOLD/Views/Pickers/RunwayPicker.swift
index ceca41b..66f7f13 100644
--- a/SF50 TOLD/Views/Pickers/RunwayPicker.swift	
+++ b/SF50 TOLD/Views/Pickers/RunwayPicker.swift	
@@ -1,4 +1,5 @@
 import SF50_Shared
+import SwiftData
 import SwiftUI
 
 struct RunwayPicker: View {
diff --git a/SF50 TOLDTests/NavDataSelectionPruningTests.swift b/SF50 TOLDTests/NavDataSelectionPruningTests.swift
new file mode 100644
index 0000000..3fe594b
--- /dev/null
+++ b/SF50 TOLDTests/NavDataSelectionPruningTests.swift	
@@ -0,0 +1,176 @@
+import Defaults
+import Foundation
+import SF50_Shared
+import SwiftData
+import Testing
+
+@testable import SF50_TOLD
+
+/// A leg's airport is remembered in the app group as a record ID, and the FAA retires airports
+/// between cycles. Installing a dataset that no longer carries one has to forget the selection,
+/// while a dataset that still carries it must leave the selection alone — a prune that fired on
+/// every install would cost the pilot the airport chosen for the flight.
+///
+/// The check opens the generation being installed rather than the container the views hold, so
+/// these tests hand the view model a store on disk and write the incoming dataset where production
+/// writes it. A view model given an in-memory store reads back the container it was handed, which
+/// is not the path this behavior takes on a device.
+@Suite(.serialized)
+@MainActor
+struct `Selection Pruning on Install` {
+  private static let carriedAirport = "CARRIED", retiredAirport = "RETIRED",
+    selectedRunway = "18"
+
+  /// The generation the view model's own container reads: the dataset being replaced.
+  private static let supersededGeneration = 1
+
+  private static func airport(recordID: String) -> Airport {
+    .init(
+      recordID: recordID,
+      locationID: "TEST",
+      ICAO_ID: nil,
+      name: "Test Airport",
+      city: nil,
+      dataSource: .NASR,
+      latitude: .init(value: 0, unit: .degrees),
+      longitude: .init(value: 0, unit: .degrees),
+      elevation: .init(value: 0, unit: .feet),
+      variation: .init(value: 0, unit: .degrees),
+      timeZone: nil
+    )
+  }
+
+  /// Selects an airport for each leg, writes a generation carrying only ``carriedAirport``, and
+  /// runs `body` against a view model whose own container reads the dataset being replaced.
+  ///
+  /// The generation is written into the app group, since that is where an install looks for it. A
+  /// process killed before the store is removed leaves one behind, which the next launch reclaims.
+  ///
+  /// `body` must not suspend. These tests are hosted by the app, whose performance view models
+  /// observe these very defaults and forget an airport ID they cannot resolve in the store they
+  /// hold — which neither of these IDs resolves in. Nothing of theirs can interleave while the
+  /// body stays synchronous on the main actor.
+  ///
+  /// - Parameters:
+  ///   - takeoff: The record ID selected for the takeoff leg.
+  ///   - landing: The record ID selected for the landing leg.
+  ///   - body: Runs with the view model and the generation being installed.
+  private static func withInstalledGeneration(
+    takeoff: String,
+    landing: String,
+    _ body: (NavDataLoaderViewModel, Int) throws -> Void
+  ) throws {
+    let selections = LegSelections.current(),
+      generation = NavDataStoreInstaller(layout: .appGroup).reserveGeneration()
+    defer {
+      selections.restore()
+      StoreLayout.removeStore(at: StoreLayout.appGroup.navStoreURL(generation: generation))
+    }
+
+    try write(carriedAirport, toGeneration: generation)
+    Defaults[.takeoffAirport] = takeoff
+    Defaults[.landingAirport] = landing
+    Defaults[.takeoffRunway] = selectedRunway
+    Defaults[.landingRunway] = selectedRunway
+
+    let viewModel = NavDataLoaderViewModel(container: try supersededContainer())
+    try body(viewModel, generation)
+  }
+
+  /// A temporary store standing in for the dataset the install is replacing.
+  ///
+  /// It holds a dataset that reads as current, so the view model's launch-state poll settles on
+  /// its first pass rather than running for the rest of the test process. The store is left on
+  /// disk for the same reason: that poll outlives the test, and one reading a store deleted
+  /// underneath it turns into an error reported every half second.
+  private static func supersededContainer() throws -> ModelContainer {
+    let layout = StoreLayout(
+      baseDirectory: FileManager.default.temporaryDirectory
+        .appending(path: "SelectionPruningTests-\(UUID().uuidString)")
+    )
+    let context = ModelContext(
+      try AppStore.makeWritableContainer(layout: layout, generation: supersededGeneration)
+    )
+    context.insert(airport(recordID: carriedAirport))
+    context.insert(
+      Cycle(dataSource: .nasr, name: "TEST", effective: .distantPast, expires: .distantFuture)
+    )
+    try context.save()
+    return context.container
+  }
+
+  private static func write(_ recordID: String, toGeneration generation: Int) throws {
+    let context = ModelContext(
+      try AppStore.makeWritableContainer(layout: .appGroup, generation: generation)
+    )
+    context.insert(airport(recordID: recordID))
+    try context.save()
+  }
+
+  @Test
+  func `forgets a takeoff airport the incoming dataset dropped`() throws {
+    try Self.withInstalledGeneration(
+      takeoff: Self.retiredAirport,
+      landing: Self.carriedAirport
+    ) { viewModel, generation in
+      viewModel.clearSelectionsMissing(fromGeneration: generation)
+
+      #expect(Defaults[.takeoffAirport] == nil)
+      #expect(Defaults[.takeoffRunway] == nil)
+      #expect(Defaults[.landingAirport] == Self.carriedAirport)
+      #expect(Defaults[.landingRunway] == Self.selectedRunway)
+    }
+  }
+
+  @Test
+  func `forgets a landing airport the incoming dataset dropped`() throws {
+    try Self.withInstalledGeneration(
+      takeoff: Self.carriedAirport,
+      landing: Self.retiredAirport
+    ) { viewModel, generation in
+      viewModel.clearSelectionsMissing(fromGeneration: generation)
+
+      #expect(Defaults[.landingAirport] == nil)
+      #expect(Defaults[.landingRunway] == nil)
+      #expect(Defaults[.takeoffAirport] == Self.carriedAirport)
+      #expect(Defaults[.takeoffRunway] == Self.selectedRunway)
+    }
+  }
+
+  @Test
+  func `keeps a selection the incoming dataset still carries`() throws {
+    try Self.withInstalledGeneration(
+      takeoff: Self.carriedAirport,
+      landing: Self.carriedAirport
+    ) { viewModel, generation in
+      viewModel.clearSelectionsMissing(fromGeneration: generation)
+
+      #expect(Defaults[.takeoffAirport] == Self.carriedAirport)
+      #expect(Defaults[.takeoffRunway] == Self.selectedRunway)
+      #expect(Defaults[.landingAirport] == Self.carriedAirport)
+      #expect(Defaults[.landingRunway] == Self.selectedRunway)
+    }
+  }
+
+  /// The defaults a leg selection lives in, captured so one test's selections cannot reach
+  /// another's.
+  private struct LegSelections {
+    let takeoffAirport, takeoffRunway, landingAirport, landingRunway: String?
+
+    static func current() -> Self {
+      .init(
+        takeoffAirport: Defaults[.takeoffAirport],
+        takeoffRunway: Defaults[.takeoffRunway],
+        landingAirport: Defaults[.landingAirport],
+        landingRunway: Defaults[.landingRunway]
+      )
+    }
+
+    func restore() {
+      Defaults[.takeoffAirport] = takeoffAirport
+      Defaults[.takeoffRunway] = takeoffRunway
+      Defaults[.landingAirport] = landingAirport
+      Defaults[.landingRunway] = landingRunway
+    }
+  }
+}