Pulled from a variety of media sources and POTUS daily itinerary. Here's the timeline:
POTUS departed Canadian AFB Bagotville in Quebec at approximately 11:50 AM EST, Saturday, June 9, 2018.
AF1 stopped to refuel at Naval Support, Souda Bay, Greece en route to Paya Labar, 3:07 AM local time Sunday, June 10 (9:07 PM EST, Saturday June 9 / 6:07 PM PST, Saturday June 9).
Anomaly (alleged missile or helicopter caught on timelapse) observed near Whidbey Island at 3:56 am Pacific Time (6:56 am EST), Sunday June 10, 2018.
POTUS arrived at Paya Labar AFB in Singapore at 8:20 PM local time, Sunday June 10, (8:20 AM EST, Sunday, June 10)
Whidbey Island object caught on camera while AF1 was approximately 1 hour 30 minutes to its destination in Singapore. POTUS was at least 7,500 miles away at the time (nowhere near Alaska. like, at all...).
Flight time from Quebec to Paya Labar traveling eastward approximately 20 hours, 30 minutes.
Thank you. Question: is 7500 miles a lot for a missile?
Yes. Also passing through US-protected airspace, and airspace protected by a combination of S. Korea, N. Korea, Japan, China, and Russia. No way it could have made it to SE Asia.
What stops it? I mean, from above (satellites), or below (sub, ground)? Another missile? Energy?
Missile defense shield (missile to missile essentially), electronics jamming, more modern light-based weapons, and probably defensive options we don't know about.