Spohr said that both airlines will sign the agreement later in the day in Berlin.
“Today is a big day, which we will seal in a few hours with a signature,” he said.
Air Berlin declared bankruptcy in August following years of losses and the decision of its biggest shareholder, Gulf airline Etihad, to cease financing.
It had been in talks for weeks with Lufthansa and easyJet about selling parts of its business.
Air Berlin had been Germany’s second-biggest carrier after Lufthansa. The airline carried some 80,000 people a day mostly on short-haul destinations. It made a loss of about 782 million euros last year.
After Air Berlin filed for bankruptcy, the German government gave the airline a 150 million euro government loan to stay afloat while it was negotiating possible deals with Lufthansa and others.
Earlier this week, dpa reported that the airline said in a letter to employees that flights under the airline code AB “according to the current state of things, will no longer be possible after October 28 at the latest.”
The details of the purchase agreement have yet to be revealed.