Air New Zealand says most of the small Eagle Airways fleet will remain grounded on Wednesday while it consults with the manufacturer after cracks were found.
Eagle Airways, a subsidiary of Air New Zealand, operates 18 Beech 1900D aircraft to about 20 domestic airports including Kerikeri, Hawke's Bay and Gisborne.
Engineers were doing checks during routine maintenance of one aircraft when a small crack was found on the tail. The rest of the fleet was then checked.
Air New Zealand says four of the aircraft will fly on Wednesday but the rest will stay on the ground while it consults with the manufacturer about any further maintenance work.
The airline will not comment on whether all of the 14 grounded planes have cracks.
It says about 1000 passengers could be affected by the grounding and other Air New Zealand planes will fill the gaps on Wednesday.
The regional airline's general manager, Carrie Hurihanganui, says the cracks are not significant, but it is taking a precautionary approach by grounding the whole fleet.
She says repairs could take up to two weeks to complete.