CREATE TABLE aircraft (aircraft_id DECIMAL, order_year DECIMAL, manufacturer TEXT, model TEXT, fleet_series TEXT, powertrain TEXT, fuel_propulsion TEXT)
CREATE TABLE pilot (pilot_id DECIMAL, pilot_name TEXT, rank DECIMAL, age DECIMAL, nationality TEXT, position TEXT, join_year DECIMAL, team TEXT)
CREATE TABLE pilot_record (record_id DECIMAL, pilot_id DECIMAL, aircraft_id DECIMAL, date TEXT)

Show the most common nationality of pilots.
SELECT nationality FROM pilot GROUP BY nationality ORDER BY COUNT(*) DESC LIMIT 1
SELECT "nationality" FROM "pilot" GROUP BY "nationality" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 1