multiple flashes like explosions in distant night sky, no sounds, nothing on police or fire scanners.

Witnesses in two separate cars driving from Lummi Reservation on to I-5 and into Bellingham, we both saw multiple distant flashes in the sky that happened in short strobe like bursts.  Lit up the entire far sky and illuminated cars etc. passing by.  Saw it again on freeway heading South toward bellingham.  Flashes like explosions but police scanner and fire scanner had nothing about fires, explosions etc.  
Also a large spotlight was being used at the Bellingham airport as we passed by and saw the flashes.  Seen again in Bellingham.  So bright I was on the far side of a building and the flashes lit up the walls of the adjacent buildings.  No sounds. Light cloud coverage, no rain.  
These flashes were extremely bright/ powerful like explosions yet no evidence of explosions, just bright flashes in the distant sky.
Witness elects to remain totally anonymous; provides no contact information.  The Bellingham Airport has a strobe-light night landing system, which is very bright., and could have been the cause of the sighting.  PD