The Air Force says it was not prepared for the tens of thousands who flocked to the Royal New Zealand Air Force 75th Anniversary Show at the weekend.
Roads leading to the air base at Ohakea were gridlocked with traffic for hours as up to 70,000 headed to the event.
An Air Force spokesperson says organisers expected just 50,000 and it is investigating to see what went wrong.
The spokesperson says the Air Force worked closely with police and hired a company specifically to organise traffic management.
Ticket holders who missed out can seek refunds from Monday.