A new study shows Whangarei airport will become obsolete within the next 15 years.

Whangarei District Council will decide next week whether building a new airport should be in its long term plan.

Infrastructure and Services Group Manager Simon Weston says there are several reasons the life span of the airport at Onerahi has become shorter than expected.

"So it's a cumulative iss associated with the industry slowly moving towards larger aircraft and the issues to do with the surrounded typography and the the CAA requirements."

Simon Weston says just extending the runway will be more costly than building a new airport.