Heathrow – approx. 40 mins: from December 2019 a total of six Elizabeth line trains per hour will serve Heathrow Terminals; four will go to Terminals 2, 3 and 4 and two will go to Terminals 2, 3 and 5.
Gatwick – Thameslink trains from Farringdon run through the night from London stations to London Gatwick Airport. With 4 trains per hour in the daytime, journey time is 50 minutes from Farringdon.
When the Elizabeth line opens in 2018 Farringdon station will be one of the busiest in the UK, connecting with Thameslink and the London Underground to provide links with outer London, the Home Counties, the City, Canary Wharf and three of London’s five airports.