A 28-plane airline, which earlier this year sparked a fare-cutting in the South and West, asked the Civil Aeronautics Board today for permission to fly between Washington-Baltimore and Houston and to charge up to 50 per cent less than current airlines do.

Texas International Airlines, whose "fly for peanuts" fares would reduce a one-way coach fare from $122 to $61 on some flights, said Washington-Houston travelers could collectively save more than $5 million the first year.

With connections to and from other cities, including Mexico City Texas International said through-travelers could also achieve additional savings with a change here to other low-fare flights.

The propsals, if approved by the CAB, could lead to competitive fare cutting by Delta and Eastern Airlines, who currently are authorized provide nonstop service between Washington and Houston.

"We will always be competitive, within reason," said a spokesman for Delta, which earlier this year reduced fares on some flights between Shreveport. La. and Dallas after Texas International cut its fares.

The TIA request comes at a time of growing sentiment for deregulation of the airline industry, whose basic fares and routes are controlled by the government, as well as growing experience that reduced fares are more than offset by increased passengers.

Texas International, for example, says it is flying almost 25 per cent more passengers this yeare than last with profits up 165 per cent. The little states and Mexico City, estimates that the reduced fare, Washington-Houston service would generate $3.7 million in new profits the first year.

The airline proposed that its new, discount service operate between Houston and Baltimore-Washington International Airport, which currently has no nonstop link with Houston. Delta and Eastern fly nonstop out of Dulles International Airport in suburban Virginia. Restrictions by the federal government do not allow nonstop service between Washington's National Airport and cities as far away as Houston, so flights between here and National generally are routed through Atlanta.

An estimated 140,000 people are expected to fly between Washington and Houston this year. Texas International, however, says it foresees 158,428 passengers "flying for peanuts" the first year as discount fares become available to the 5 million people of the Washington and Baltimore metropolitan areas and the 3 million people of greater Houston.

Beyond that, the airline envisions the lower fares drawing people from within 150 miles of BWI airport - from Virginia, Delaware and Pennsylvania including some people who now may drive to Philadelphia.

Frank Lorenzo, Texas International's president, said the peanut fares have taken people from automobiles and "the sofa" - the people who wouldn't otherwise travel.

By comparison, a one-way Greyhound ticket between Houston and Washington costs $75 and takes 39 hours. The Texas International flights would take two hours and 45 minutes and cost $61 or $79 or $98 - reductions of 50 per cent. 35 per cent and 20 per cent, depending on the time of day and day of the week.

The closet existing rate is a $98 night flight offered by Delta.

Texas International which has been involved in a Texas air-fare war for years, said it could begin service within 90 days but that CAB proceedings would delay the service until 1979, if the CAB eventually approves it.

Delta and Eastern are expected to oppose the request. "We're going to try to protect any authority we have." said the Delta spokesman.

Approval of the service would mark the entry of Texas International into the Northeast and give Washington and Baltimore residents a taste of the fare cutting that has been going on here. In a state where major cities lie so far apart (you can fly on a jetliner here for two hours and 26 minutes and still be in Texas), low-fare flights have become extremely popular.

It is not unusual to be able to fly someplace for less than the gasoline for an auto. TIA, for example offers a $15 Houston-Dallas ticket for its five-abreast seating on red, white and blue DC-9 twin-jets.

Much of the airfare competition here has been forced by Southwest Airlines, a feisty state-regulated airline with stewartdesses in shorts and boots which flies only in the state.

But early this year, TIA won permission from the CAB to try its peanuts fares. It cut rates first on five routes, and today the airline offers reduced rates on more than half of its 200-plus daily flights.

It has capitalized heavily on the election of a Georgia peanut farmer as president. At today's announcement of the Houston Washington preposal, the airline displayed a cartoon of a Carter-like family of peanuts, complete with broad grins. In front of the White House, Washington Monument and Capitol. Amy Peanut says. "We got here for peanuts," and President Peanut says, "Now you can, too."