Texas International Airlines yesterday announced new fare discounts of up to 78 percent on its flights from Baltimore/Washington International Airport, bringing some fares down to levels it says are cheaper than the lowest bus prices.

TI also announced a new, unrestricted $99 fare between BWI and Dallas/Fort Worth, good on all its flights, effective yesterday.

An official of the airline said that the highly discounted tickets, once purchased, cannot be transferred to another person, reissued for another flight or returned for a refund. Tickets also must be purchased when the reservations are made, at least 14 days before departure. The number of seats at the "bus" fares are limited but there are a substantial number of them on every flight, he said.

Under the program, travelers will be able to fly one way to Hartford/Springfield for $39, to New Orleans for $78, to Houston for $79, and to Albuquerque, Los Angeles and San Antonio for $98. Some of TI's flights from BWI are nonstop.

The TI fares, on sale today through March 8, are good for travel between Feb. 23 and April 7.

In another development in the continuing transcontinental fare battle, World Airways said it was dropping its one-way fare to $139.