When British Prime Minister John Major visited President Bush at Camp David last December, he had two major discussion items on his agenda, and both concerned war.

Item number one: the war in the Persian Gulf.

Item number two: the "war" over routes to London's Heathrow Airport; increased opportunity for British Airways to fly to--and within--the United States, and the battle for foreign ownership of U.S. airlines.

If Major and other foreign interests get some or all of what they want, experts say that it would initially mean more airlines for American travelers to choose from, but in the longer run could lead to the demise of some U.S. carriers, higher fares and the curtailing or abolishing of frequent-flier programs--in effect, fewer choices and higher prices.

The first development in the transatlantic airline war was United Airlines' announcement Oct. 23 that it would pay cash to acquire Pan Am's London routes at Heathrow. Shortly thereafter, TWA announced that it would be selling its London routes to American for $515 million.

Although the U.S. Department of Transportation tentatively approved both transactions in January, British Airways is clearly not happy with either deal, since United and American figure to be more competitive with British Airways than either Pan Am or TWA, due to more extensive route systems within the United States.

Liam Strong, British Airways' director of marketing and operations, said that allowing United into Heathrow without getting concessions in return from the United States would be "a very dangerous precedent."

So, what does British Airways want?

--It wants more flights into the United States, and then on to other countries.

--It wants to be able to serve all major American cities from Heathrow (combined, U.S. and British airlines now serve about a dozen).

--It, and other international carriers, want cabotage rights--i.e, to serve some American cities from other American cities. Currently, U.S. statutory law doesn't allow foreign airlines to operate over domestic routes.

If that law were changed, it would mean that in addition to the choice of domestic airlines on the route between, say, Los Angeles and New York, passengers could also fly British Airways or Air France. On flights between San Francisco and Chicago, passengers could also choose Lufthansa. Or between Minneapolis and Washington, KLM.