The onboard Microwave Landing System has been installed on 29 of the airline's Airbus A320s and A321s with the remaining 12 to be completed by the end of 2009.
British Airways claims to be the first commercial airline to introduce the system.
On average, there are 10 foggy days each year at Heathrow, which result in air traffic control having to reduce the number of aircraft landings, leading to delays, diversions and cancellations.
Periods of intense rain can also lead to restrictions on the normal landing rate.
Captain Stephen Riley, director of flight operations at British Airways, said: 'This initiative will mean less disruption and congestion, and also reduce holding times for aircraft, which will cut unnecessary carbon emissions.'
In foggy conditions, pilots use Instrument Landing Systems (ILS) to guide the aircraft onto the runway. However, ILS is susceptible to interference from other aircraft crossing in front of the runway transmitters so air traffic control has to increase the space between the landing aircraft to protect the ILS signals.
Aircraft equipped with the Microwave Landing System can make their landing approaches without the need for additional air traffic spacing.
The Airbus A320 family is the first commercial aircraft range to be certificated by the European Aviation Safety Agency (EASA) to operate the new system.