From Alpha83:
"Russia closed, among many others bordering Ukraine, a segment of the A87 airway (this particular segment was on flight 17's route, just minutes away before the shootdown) by NOTAM as of 0000Z on July 17th, i.e. more than 12 hours before the crash."
Specifically the A87 segment was the continuation in Russia of the L980 Ukraine route MH17 was flying.
Some airlines' flights in the past week, Air France and BA in particular on routes to Bangkok had been avoiding eastern Ukraine while others had not (including a bit surprisingly KLM of Air France-KLM on flight to Kuala Lumpur).
Article and maps courtesy of the NY Times at
http://www.nytimes.com/interactive/2...ight-mh17.html