WHEN EDWIN L. COLODNY suggested on Tuesday that Andrews Air Force Base might be a good place to put commercial shuttle flights to New York and elsewhere, the man from Eastern Airlines spilled his coffee. There was amazement in the aviation world at the ideas about air transportation in Washington which were tossed out by the chairman of USAir. One of their own had dared to embrace the thought that National Airport is not sacred.

Mr. Colodny went even further. He said the federal government should consider improving the facilities at Dulles Airport and then closing National and putting something other than an airport on that prime real estate. Such an idea must be the ultimate heresy in that circle -- in which 24 airlines are currently trying to jam 812 flights a day into National while Dulles remains practically vacant.

Such proposals are not new. More than a decade ago, the Air Force scotched the idea that Andrews ought to be used for something other than an occasional military and presidential flight. And Congress, with much support from the airlines, has regularly rejected any plan that might reduce air traffic at National and make life in this city more pleasant.

But the source and timeliness of these proposals are important. Mr. Colodny is a man to be reckoned with in his business. His airline (it used to be called Allegheny) operates about 15 percent of the flights at National. His suggestions come just as the Reagan administration begins to grapple with its first National Airport problem. A new set of rules goes into effect there in April unless Congress votes them down or Secretary of Transportation Lewis withdraws them.

Secretary Lewis could do nothing more beneficial for this city than to take a cue from Mr. Colodny and start the process of closing National. It makes no sense to fill in another part of the river, build a new terminal complex and revamp the highway network there while the weeds grow at Dulles and Andrews. Yet that is what the future holds if the airlines, except for USAir, and certain powerful members of Congress have their way.

Mr. Lewis might even find in this subject a remarkable opportunity to help President Reagan fulfill that promise to diminish the size of the federal government. It could get out of the business of operating commercial airports completely by selling, leasing or giving National and Dulles to a Virginia or regional airport authority.

Given the devotion Congress has shown to National down through the years, that solution to the area's air transportation problem may seem an impossible dream. But given a new beginning, who can tell? We would'nt have believed, just last week, that an executive of a major airline would publicly embrace the idea that National Airport should become a memory.