Mesa CRJ7 near Wilmington on Jan 29th 2014, air conditioning problems and smoke

A Mesa Airlines Canadair CRJ-700 on behalf of United, registration N506MJ performing flight YV-3759/UA-3759 from Washington Dulles,DC to Boston,MA (USA) with 61 passengers and 4 crew, was climbing through about FL280 about 10nm southeast of Philadelphia,PA when the crew initiated a rapid descent due to problems with the air conditioning systems. The aircraft turned around and diverted to Wilmington,DE for a safe landing on runway 01 about 25 minutes later.

The FAA reported smoke on board of the aircraft.