Japan's new passenger jet on Sunday aborted a test flight to the United States for the second time in two days because of an air conditioning defect, its maker said.

On Saturday a Mitsubishi Regional Jet (MRJ) left Nagoya airport in central Japan for the US but soon turned back due to air conditioning problems.
The plane took off again on Sunday but problems "in the same air conditioning monitoring system" caused it to return, Mitsubishi Heavy and its subsidiary Mitsubishi Aircraft said in a joint statement.
"After the jet returned yesterday, we checked the system and changed parts. After confirming that there was no problem in a test on the ground, today we launched the flight again, but the same problem occurred," company spokesman Yuji Sawamura told AFP.
The development of the MRJ, Japan's first domestically produced passenger jet for over half a century, has suffered a series of delays.
In December Mitsubishi Heavy said it was postponing delivery of the planes by one year to the second quarter of 2018 for system software upgrades and other design changes.
The twin-engine MRJ marks a new chapter in the country's aviation sector, which last built a commercial airliner in 1962 -- the YS-11 turboprop that was discontinued about a decade later.
Japan's MRJ will compete with other regional passenger jet manufacturers such as Brazil's Embraer and Canada's Bombardier.
Mitsubishi Heavy unveiled the jet -- which is about 35 metres (115-feet) long and seats about 80 passengers -- in October last year and has received more than 400 orders.