Southwest Orders 34 Boeing 737s : Aviation: The deal is valued at $1.2 billion. Planes will be delivered starting in 1995.

SEATTLE — Boeing Co. Thursday said Southwest Airlines has ordered 34 of its 737 aircraft in a transaction valued at about $1.2 billion.

Dallas-based Southwest will convert 30 options to firm orders and place four new orders, all for delivery between 1995 and 1997, Boeing said.

Southwest also placed a $240-million order to buy engines for the planes from CFM International, a joint company of General Electric Aircraft Engines and SNECMA of France, GE said.

Low-cost, no-frill Southwest operates only Boeing 737s and was the first customer for both new-generation models, the 737-300 and the 737-500, Boeing said.

Southwest’s latest order brings total orders for the 737 family of aircraft to 3,019, Boeing said. More than 130 customers outside the United States and 25 U.S. airlines operate 737s.

The 737 is a narrow-body aircraft with a range of 2,500 to 3,000 miles. The 737-300 model seats 128 passengers in two classes and the 739-500 seats 108, a Boeing spokeswoman said.

Southwest began ordering 737s about 21 years ago, Boeing said.

“The 737 has evolved along with Southwest and has played a key role in helping us establish a strong, profitable position in a very tough market,” Herbert Kelleher, the airline’s chairman and chief executive, said in a statement.

Southwest, which serves several Southwestern, Western, and Midwestern states, offers a single class of service at low fares.

The airline has avoided the fare wars that have slashed revenue at other U.S. airlines, including large carriers such as American, United and Delta.

Southwest said its net income increased 122.2% to $23.5 million in the second quarter, while American, United and Delta all reported wide losses.

With the Southwest order, Boeing has received 147 firm orders for aircraft during 1992, including 78 737s; 17 747 wide-body long-range aircraft; 15 757 wide-body medium-range aircraft; and seven 767s, a wide-body, medium-range aircraft that comes in an extended-range version.

Boeing also received orders for 30 777s, a new wide-body aircraft with a range of more than 6,500 miles. The first 777 will go into service in 1995.