Key Points:

Memo to Air Force - close windows on incredibly expensive Skyhawks or they will get wet inside.

The RNZAF issued a statement today saying Safe Air Ltd, which maintains the fleet, found rainwater had got into four of the 17 Skyhawks at Base Woodbourne, near Blenheim.

Parachute packs got damp and some instruments were a bit wet so components were removed and serviced.

There was no damage or impact on the sale or resale value of the aircraft.

"The cause of water entry is not a failure of the Skyhawks protective coat but is likely to be the improper re-sealing of cockpit canopies after a routine maintenance inspection," the statement said.

Act MP Heather Roy raised the issue. She understood the latex covers on the planes were ineffective and the cockpits were found mouldy and with water pooled inside.

She said damage included making ejection seats unsafe, corrosion and ruined avionics.

The planes have been on the market for seven years after the Government decided to scrap the military's air strike capability.

Under the terms of the original purchase of the planes from the US government it has to approve their resale and this has not yet been granted.

- NZPA