From King’s Cross St Pancras, take the Piccadilly line directly; if crowded

https://charliellav811.tearosediner.net/bus-routes-to-heathrow-airport-local-services-night-buses-and-fares

From King’s Cross St Pancras, take the Piccadilly line directly; if crowded, consider one stop on the Circle/Hammersmith line to an easier interchange at Paddington.