Texas International Airlines yesterday announced a new program that will provide relief for air travelers who have wearied of calling around to find the lowest fare between two cities.

"We're setting up a clearinghouse of lowest-fare information for nationwide flights and a bank of toll-free WATS numbers for consumers from coast to coast," Texas International President Robert D. Galloway said yesterday.

Galloway said the consumer will be able to obtain information on the lowest possible air fare not only between cities Texas International serves, but all others as well. "If we don't serve a particular city, we will still quote the lowest fare and the carrier which offers it," he said.

The toll-free numbers should be installed by March 1.

The clearinghouse is part of a series of programs announced by the Houston-based airline to take effect over the next several weeks. The other programs include:

* A guarantee to the public that, after March 1, Texas International will never be undersold and, in many cases, will give consumers a fare one-third lower than other airlines' lowest fares. If TIA fails to offer the lowest fare for comparable service in its markets, the passenger can decide what the flight should cost, "down to $1." (Also yesterday, Delta Airlines separately announced a "Delta will not be undersold" fares program offering to "instantly match" any domestic nonstop or through-jet fare available on another airline, if Delta doesn't already have the lowest discount fare.)

* The offering of an unlimited travel "Texas pass" with flat fares of $99, $149 and $249 that will provide substantial savings to frequent flyers in 11 Texas cities and New Orleans. While some other airlines have unlimited mileage programs for vacationers, this appears to be the first for business travelers. Beginning Feb. 8, a traveler flying regularly between two Texas cities could buy a $99 pass good for seven days of travel. The $149 pass allows unlimited travel for seven days to all 11 Texas cities and New Orleans. A 30-day pass to all those cities costs $249.

* Reinstitution of last year's program, providing free travel to a passenger who makes at least five roundtrip flights on TIA.