A labor union representing air traffic controllers in Japan has called for a "significant increase" in staff to improve the safety of operations at airports in the wake of a deadly crash at Tokyo's Haneda Airport last month.

The statement issued late on Tuesday by the chair of the transport workers' union executive committee did not say staffing issues contributed to the Jan. 2 crash between a Japan Airlines (JAL) jet and a smaller Coast Guard turboprop.

An investigation is ongoing into the runway collision at the world's third-busiest airport in which all 379 people on board the Airbus A350 passenger jet survived, but five of the six crew on the smaller Coast Guard aircraft died.