U.S. Forces Japan, based at Yokota Air Base, was supposed to see the arrival of three CV-22 Ospreys this year, but they’re now scheduled to arrive in 2020, reports Stars and Stripes.

Yokota Air Base is expected to accommodate a Special Operations Squadron with 10 Ospreys, adding 1,100 personnel to the installation’s population of 11,500.

Originally announced to arrive in the fourth quarter of fiscal year 2017, DOD now expects their permanent arrival in fiscal year 2020,” the Defense Department said in a statement on Monday.

The Osprey “will increase interoperability, enhance operational cooperation, and promote stronger defense relations with the Japan Self-Defense Forces,” the Pentagon said back in May 2015.

Yokota officials did not provide reasons for the delay, according to Stars and Stripes. Local residents have protested the plan to add aircraft and personnel.