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Two US Airways flights stymied by mystery odors

Mystery smells caused problems on two separate US Airways flights on Wednesday.

Passengers on Flight 439 from Philadelphia to Las Vegas had to switch aircraft after a persistent odor was detected. The flight, carrying 134 passengers, was delayed nearly six hours, Valerie Wunder, a spokesperson for US Airways, told msnbc.com.

The flight crew detected an odor before takeoff, and the plane returned to the gate, Wunder said. Later, after the jet took flight, the crew noticed the odor once again, and the plane returned to Philadelphia International Airport, where US Airways swapped out the aircraft. 

In a separate instance, four flight attendants were transported from Florida’s Fort Lauderdale-Hollywood International Airport to a hospital as a precautionary measure after a smell onboard a US Airways plane made them feel ill, Wunder said.

The odor was caused by the overservicing of the auxiliary power unit, Wunder said. As a precaution, the flight crew called paramedics.

The local fire department opted to call in a hazardous materials team, Wunder said. Readings taken came back negative, according to a report on NBC Miami.

Joe Myxter has been running msnbc.com's Travel section since 2006. Follow him on Twitter.