Long-plagued by technical faults, four Spanish-made CASA military transport planes bought by the Czech army have been cleared to fly combat missions, the defence minister said Monday.

The CASA C-295M planes, bought in 2010, had been grounded for combat missions after failing anti-missile protection tests but were still approved for training and transport flights.

"Tests of the DAS (anti-missile protection) system have shown very good results," Czech Defence Minister Vlastimil Picek told reporters.

"At present, the Czech army has four full-fledged transport planes usable for a full spectrum of operations in the Czech Republic and abroad."

He said the aircraft passed the tests on Friday.

The Czech Republic, which joined NATO in 1999, bought the planes to replace obsolete Soviet-made Antonov An-26s in a deal worth 134.5 million euros ($175.5 million).

Experts and local media slammed the contract as overpriced and suggested corruption may have played a role.

Last year, police asked parliament to strip former defence minister and now lawmaker Vlasta Parkanova of immunity. She was later charged with abuse of power in connection with the contract.

In their non-combat capacity, the planes were notably used to transport rare Przewalski's horses from the Prague zoo to Mongolia to reintroduce the critically endangered species to its homeland.