Atlanta-based Delta Air Lines announced it is buying 40 new 76-seat regional jets from Bombardier Aerospace, as part of an ongoing effort to replace smaller regional jets.

As part of the move announced Thursday to buy more CRJ-900 regional jets with economy class and first class, Delta is phasing out 60 of its smaller CRJ-200 jets, which have 50 seats. The new CRJ-900s will begin arriving in the second half of 2013, to be operated by Delta Connection regional carriers.

Delta’s order also includes options for 30 additional CRJ-900s, according to Bombardier. The aircraft manufacturer said based on the list price for the aircraft, Delta’s order is worth about $1.85 billion for the 40 firm orders and up to $3.29 billion including the options.

Delta already has 101 CRJ-900s in its fleet. The newer, larger regional jets are more fuel-efficient, less costly to maintain and better liked by customers than the 50-seat regional jets. Because the larger jets are replacing smaller ones, Delta said the move will not add to its flying capacity, and will instead keep it the same.

The CRJ-900 purchase is in addition to Delta’s lease of Boeing 717-200s from Southwest Airlines, which acquired AirTran Airways, and Delta’s purchase of Boeing 737-900ER jets. Those planes will also replace other aircraft Delta is retiring from its fleet.