diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6e6fb2c..9666444 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - "Copy details" button on each route card — copies the route path, fee,
   and time as plain text to the clipboard (resolves #21).
+- Loading state while routes are being calculated: short artificial delay
+  plus spinner, stylable ahead of Phase 2's real network calls (resolves #16).
 - Unit test for `availableCurrencies()` (resolves #27).
 - Component tests for `RouteList` covering the not-searched, empty, and
   populated states (resolves #25).
diff --git a/src/App.jsx b/src/App.jsx
index c750245..092a9b5 100644
--- a/src/App.jsx
+++ b/src/App.jsx
@@ -13,19 +13,25 @@ export default function App() {
   const [searched, setSearched] = useState(false)
   const [lastQuery, setLastQuery] = useState(null)
   const [engineError, setEngineError] = useState(null)
+  const [loading, setLoading] = useState(false)
 
   const currencies = availableCurrencies()
 
-  function handleSubmit({ fromCurrency, toCurrency, amount }) {
+  async function handleSubmit({ fromCurrency, toCurrency, amount }) {
+    if (loading) return
     setEngineError(null)
+    setSearched(false)
+    setLoading(true)
     try {
+      await new Promise((resolve) => setTimeout(resolve, 500))
       const found = findRoutesCached({ fromCurrency, toCurrency, amount, anchors: mockAnchors })
       setRoutes(found)
       setLastQuery({ fromCurrency, toCurrency, amount })
       setSearched(true)
     } catch (err) {
       setEngineError(err.message)
-      setSearched(false)
+    } finally {
+      setLoading(false)
     }
   }
 
@@ -51,7 +57,14 @@ export default function App() {
           </p>
         )}
 
-        <RouteList routes={routes} searched={searched} />
+        {loading ? (
+          <div className="loading" role="status">
+            <span className="spinner" aria-hidden="true" />
+            Finding routes…
+          </div>
+        ) : (
+          <RouteList routes={routes} searched={searched} />
+        )}
       </main>
 
       <footer>
diff --git a/src/styles.css b/src/styles.css
index 25e31d9..f11cbd0 100644
--- a/src/styles.css
+++ b/src/styles.css
@@ -129,6 +129,29 @@ header h1 {
   padding: 1rem;
 }
 
+.loading {
+  display: flex;
+  align-items: center;
+  gap: 0.6rem;
+  color: var(--muted);
+  padding: 1rem 0;
+}
+
+.spinner {
+  width: 1.1rem;
+  height: 1.1rem;
+  border: 2px solid var(--border);
+  border-top-color: var(--accent);
+  border-radius: 50%;
+  animation: spin 0.8s linear infinite;
+}
+
+@keyframes spin {
+  to {
+    transform: rotate(360deg);
+  }
+}
+
 .route-list {
   list-style: none;
   margin: 0;
diff --git a/tests/App.test.jsx b/tests/App.test.jsx
new file mode 100644
index 0000000..22b57cc
--- /dev/null
+++ b/tests/App.test.jsx
@@ -0,0 +1,54 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+import { act } from 'react'
+import { createRoot } from 'react-dom/client'
+import App from '../src/App'
+
+function setup() {
+  const container = document.createElement('div')
+  document.body.appendChild(container)
+  const root = createRoot(container)
+  act(() => {
+    root.render(<App />)
+  })
+  return { container, root }
+}
+
+function cleanup(root) {
+  act(() => {
+    root.unmount()
+  })
+}
+
+beforeEach(() => {
+  vi.useFakeTimers()
+  globalThis.IS_REACT_ACT_ENVIRONMENT = true
+})
+
+afterEach(() => {
+  vi.useRealTimers()
+  globalThis.IS_REACT_ACT_ENVIRONMENT = false
+  document.body.innerHTML = ''
+})
+
+describe('App loading state', () => {
+  it('shows a loading indicator while routes are being calculated, then results', async () => {
+    const { container, root } = setup()
+    const form = container.querySelector('.remittance-form')
+
+    await act(async () => {
+      form.dispatchEvent(new Event('submit', { bubbles: true, cancelable: true }))
+      await Promise.resolve()
+    })
+
+    expect(container.querySelector('.loading')).toBeTruthy()
+    expect(container.querySelector('.loading').textContent).toContain('Finding routes')
+
+    await act(async () => {
+      vi.advanceTimersByTime(500)
+      await Promise.resolve()
+    })
+
+    expect(container.querySelector('.loading')).toBeFalsy()
+    cleanup(root)
+  })
+})