Domestic Airlines at Heathrow Airport

The 2 main airlines who offer Domestic flights from London Heathrow Airport are British Airways and BMI (British Midland)

British Airways Domestic Flights
BA flies to the following UK cities from Heathrow:

Aberdeen
Edinburgh
Glasgow
Manchester
Newcastle

BMI Domestic Flights
BMI flies to the following UK cities from Heathrow:

Aberdeen
Belfast
Durham Tees Valley
Edinburgh
Glasgow
Leeds
Manchester
Newcastle

UK domestic flight routes all operate at a high frequency.
BA Flight Timetable sets up to 8 flights a day between Heathrow and Manchester Airport
British Midland Flight Timetable sets up to 7 flights a day between London Heathrow and Manchester Airport.

BA flights to UK cities are transferring from Terminal 1 to Terminal 5, whilst BMI flights will continue to depart from Terminal 1

The UK domestic flight network from Heathrow is a high frequency full service offer. The passenger makeup includes feeder passengers from the UK regions connecting onto the Heathrow Long Haul network. The business passenger is also an important element of the short haul network.