I posed the question regarding evidence of chems used...

[Agnosticsherbet]

6. So there is no report an air attack by other natonal forces.

Something the Syrian government would know about due to this old fangled invention of radar. Also, Syria is known to have one of the most sophisticated air defense systems that an attacking Air Force would have to defeat. (That is widely reported as one of our biggest concerns, Russian made surface to air missiles.)

When Israel took out the Syrian nuclear power plant several years back, they flew in through Turkey, but Syria still knew when they crossed into their air space and engaged their air defense system. So did Turkey who went along with it.

Israel's attack earlier this year was known and reported widely. All the countries in the region knew it happened.

The reports I've seen list Syrian Air Force as the attacker.

A false flag operation on this scale is too far fetched for anything but a movie.

Everybody in the region has radar. Nobody but the US or Russia are flying stealth aircraft. (Israel is not due to receive any until 2016 http://www.algemeiner.com/2013/06/19/israel-to-be-among-first-recipients-of-new-f-35-stealth-fighter-jet/)

The easiest explanation is that Assad, out of desperation and after a series of small scale tests for a year and emboldened by Iranian and Russian support, decided that nothing would be done. Greeks called that hubris, I believe.