INSTEAD OF spending today and tomorrow getting ready for a strike, officials of the air controllers union and the Department of Transportation ought to keep talking. The strike, now scheduled for Monday morning, is unlikely to do anyone much good and will seriously incovenience, if not actually harm, many innocent bystanders.

The issue in this dispute, despite all the inflated rhetoric of recent days, is quite simple. The air controllers union wants the Reagan administration to seek from Congress more money for its members than Secretary of Transportation Drew Lewis believes is justified. The union broke off negotiations last Wednesday after it was told that a $40 million package put on the table by Mr. Lewis' negotiators was the government's final offer.

The package would give the air controllers an average pay increase, including the cost of a somewhat shortened work day, more than twice the size of the one the administration wants to give other federal workers. That's an indication, although nothing like the one the air controllers would like to have, that the government regards these employees as somewhat special. Without that, the administration would be hard put to justify any extra increase at a time when it is busily urging Congress to slash spending on almost every other front.

The difference between that offer and what the union says it wants is so vast as to be unreal. The controllers started the bargaining by demanding an immediate $10,000 raise for each worker; the typical controller now makes $32,000, and some get as much as $50,000. Their jobs do involve more stress than those of most other government employees, but there is a limit to how preferred a position in the government hierarchy they should have.

There is another aspect to this proposed strike that is even more troubling. The air controllers are barred by law from striking and are under a federal court order not to strike or the engage in slow-down tactics. For them to defy those twin injunctions, as their president has said they will, would demonstrate a contempt for the orderly processes of government so serious as to justify harsh retaliation. A union that is really demanding that Congress pass a law giving it what it wants hardly does it cause any good by ignoring another law Congress has already passed.

The place to settle this dispute is not on the picket line -- with irate airline passengers (and taxpayers) standing all around -- but at the bargaining table. Secretary Lewis has said several times in recent days that there is considerable flexibility in that "final" offer. Both sides need to explore that opening with any eye toward keeping the airplanes in the air.