United will begin a third daily service between Heathrow and its Houston hub, George Bush Intercontinental Airport, from 31 March, which will also see the introduction its Global First product on to the route.
The additional flight, UA971, will depart London at 13:35, arriving in Houston at 18:10 the same day. The return flight, UA970, will depart Houston at 20:30, arriving in London 12:05 the next day.
United will operate the flights with Boeing 767-300 aircraft with six United Global First seats, 26 fully-flat Business First seats and 151 in economy, including 67 Economy Plus seats.
The existing London to Houston flights depart at 09:20 and 11:40, arriving in Houston at 13:55 and 16:15 respectively. The return flights depart Houston at 15:40, arriving in London at 06:50 the next day and 18:30, returning at 09:40 the next day.