A 5km (3m) tunnel under the M4 and M25 would link Terminal 5 with Langley and Iver, connecting passengers via Slough to Reading and the west.
If granted planning permission, Network Rail could begin construction in 2016.
Currently, passengers travelling from the west to Heathrow Airport have to travel in to London and connect with trains from Paddington or use underground services on the Piccadilly Line.
Patrick Hallgate, Network Rail route managing director Western route said: “Our plans for a new rail link to Heathrow from the west will dramatically improving rail links, reduce congestion on existing rail services and provide a boost to the local economy. It’s important that we take the opportunity to discuss these plans so we can ensure the investment made in a bigger, better railway delivers maximum benefit.”
“Studies show that improving access to Heathrow will stimulate growth, and could deliver over £2 billion in economic benefits, over 40,000 additional jobs, and significant environmental benefits. Faster and more reliable connections will safeguard the prosperity of the Thames Valley, by putting businesses in closer contact with their global markets.
“Giving passengers the opportunity to access Heathrow by train will support sustainable growth by reducing congestion on the road network and reducing the impacts of the airport on local communities.”