The trains, whose route would closely follow that of the M25, would create a “Heathwick” aircraft hub.
Supporters of the scheme, which would cost an estimated £5bn, say it offers a cheaper solution than building a new airport in the Thames Estuary.
But critics predict that such a rail link would face considerable challenges.
A Department for Transport spokesman said: “This proposal will form a useful contribution to the debate and will be considered alongside all other responses.”
A virtual hub faces seemingly insurmountable technical, operational, political and financial challenges.BAA spokesman
Victoria Borwick, of the Greater London Authority’s transport committee, commented: “If there’s a way of helping Londoners sort out their travel needs, then this should be examined.”
She continued: “It’s good that the government are examining other alternatives to get people around.”
But a spokesman for BAA, which owns Heathrow, said a rail link would not solve the problem of runway capacity.
He warned: “A virtual hub between Heathrow and Gatwick faces seemingly insurmountable technical, operational, political and financial challenges, and would take many years to deliver.”
The scheme is to be included in the government’s review of aviation policy, to be published for consultation in the spring of 2012.