ATLANTA (AP) _ Delta Air Lines announced plans Thursday to beef up service between Atlanta and some key cities for business travelers, underscoring its push for expansion of Hartsfield Atlanta International Airport.

Leo F. Mullin, Delta's president and chief executive, said Delta was responding to strong demand by business travelers for more flights with a new schedule that adds some two dozen daily flights between Atlanta and Boston, New York, Washington, Baltimore, Chicago and Newark, N.J. The schedule is effective Oct. 1.

``Delta is responding to extraordinary demand from our customers for more service between business centers and Atlanta,'' said Mullin.

The expansion includes three new daily round-trip flights between Atlanta and Chicago's Midway Airport, augmenting Delta's service to Chicago's O'Hare airport.

Delta also will have hourly service to Boston and Newark during usual business travel hours, and is adding to its hourly service between Atlanta and LaGuardia Airport another four flights _ morning, noontime, early afternoon and early evening.

The carrier is reducing service to some small markets, leaving a net increase of 11 flights from Atlanta. That will bring Delta to a total 633 Atlanta-based daily flights.

Mullin renewed his call for Hartsfield expansion from the current four to six runways. He has said before that Delta will shift future growth to other hubs if Hartsfield's capacity isn't bolstered, but he expressed confidence Thursday about expansion here.

``I feel progress is being made,'' he said.