THE TRAVELERS caught in the British air controllers' strike are participants - involuntarily - in a crucial test of an embattled government. That thought won't make the time pass any faster for the thousands of people waiting endlessly in packed airports for their long-delayed flights to be called. But the stakes are commensurate with the inconvenience to the stranded multitudes, and that inconvenience is monumental.

By all accounts the scene in London's Heathrow Airport is reminiscent of Gustave Dore's illustrations for the "Inferno," with numberless souls packed together in attitudes of deep suffering and despair. Abandon hope, all ye who were lucky enough to hold reservations on the canceled flights Air traffic across the Atlantic tends to follow the peak of the westward surge of American students and teachers for the beginning of classes.

One small union is, in fact, holding these travelers hostage in its own quarrel with its government. But that quarrel is far from a narrow or private one. For the past two years Britain's struggle to control inflation has been based on a rigorous series of wage agreements between the government and the unions. The unions, it should be said, stuck to the agreements with remarkable discipline. But those agreements expired at the beginning this month and, having extended them once, the unions refused to do it again. There followed the uneasy truce that the air controllers have now broken.

The air-transport system is the perfect target for a strike with a political edge to it. Even a small union can create instant chaos, with an impact that a strike in, say, the steel industry would require weeks to achieve. An air strike generates immense publice pressures for a fast settlement. In this country, it was the machinists' 1966 strike against five airlines that did in the Johnson administration's wage guidelines. Last summer, on the eve of the Olympics, the air controllers in Quebec struck over the language issue. Now, in the case of the British controllers, it's a case of setting the government's wage policy in the aftermath of the negotiated compacts.

During these two years of restraint on wages, most British families have suffered a decline of considerable dimensions in their purchasing power. Wages recently have been rising only about half as fast as consumer prices. Meanwhile, of course, there has been very little economic growth. Unemployment has continued to rise. The government has lost its majority in Parliament and continues with the tiny Liberal Party. Elections, everyone assumes, are not far off.

All of that makes it a bad time for the govenment to hang on in this challenge to its determinatin - buy an even worse time to let go. As for the weary crowds in the lounges at Heathrow, they can justly complain that they did not ask for this unscheduled excursion into British economic policy. Travel once again turns out to be more educational than the travelers had expected.