flight_routes (origin, dest) lists direct flights; each row flies one way only, and many airports fly back to where they came from.
From `LHR`, find every airport you can reach in at most 4 flights, with:
- •
flights — the fewest flights needed - •
route — one route with that many flights: the airport codes from LHR onwards joined by >, e.g. 'LHR>JFK>SFO'. When several routes are equally short, return the alphabetically first.
LHR itself isn't listed, and airports that need more than 4 flights are left out.
Columns: airport, flights, route. Sort by flights, then airport.