BANGOR – Telford Aviation Inc. has sold an airplane designed for surveillance missions to the U.S. Army for $7.4 million.

The Army had leased the four-engine turboprop DeHavilland Dash-7 from Telford for two or three years before the purchase, Bob Ziegelaar, president of the Bangor-based company, said Thursday.

As part of the sale agreement, Telford will upgrade the airplane, which could include some new equipment and modifications, Ziegelaar said. The work will be performed in Maryland.