Umm, hmmm… Where to start here.
I've been routed over some very, shall we say, unsavory locales. They know we're coming, we've paid them a fair ransom for the right to do so, and largely we've got diversionary planning in order to help us either get to a more safe and/or politically safe airport if certain events transpire. Karachi does a fantastic job, for the most part, they do the best they can, but like hell I'm going to drop in there for a medical emergency.
A number of years ago, a large international carrier had an indication of a cargo fire over Iran in a DC-10. You really don't want to mess with cargo fires and the flight diverted into Tehran.
I wouldn't expect a maintenance crew to immediately fly into Iran because there are a whole number of technical and political dynamics which would be necessary. We have, well, shall we say appropriately-equipped extract options available to us worldwide, but that's intended Blackhawk Down type situations and a simple emergency diversion doesn't necessarily mean that the State Department wants to deal with the private appropriately-equipped extract option because it will be an international event which has ramifications well beyond the scope of what all of us sitting behind a computer full of vim and vigor can fathom.
I withhold judgement of Malaysian Airlines. They've got a whole lot more stuff going on than many of us, in front of our computers in the safety of the United States, possibly realize. It feels good to talk tough and talk about what someone else should do, just as long as we realize that it's just talk.
Malaysia, hell, not even you as an American, can go blazing into separatist-controlled anything. Where are you going to land? How are you going to get from where you landed to the location of the investigation without cooperation and coordination? Rambo's a movie.