Malaysia Airlines Flight 370 - Why didn't Malaysian Air Force scramble jets?
There are multiple reasons for this:

The aircraft stopped communicating after the Kula Lumpur asked the aircraft to contact Ho Chi Minh ACC. The last verbal contact with the aircraft is this:


Lumpur Radar: &quot;Malaysian three seven zero, contact Ho Chi Minh one two zero decimal nine. Good night.&quot;
Flight 370: &quot;Good night. Malaysian three seven zero.&quot;

The Kula Lumpur Control had no way of knowing whether the aircraft had contacted as instructed (and acknowledged).

According to the Malaysian defence minister, the aircraft was deemed commercial and not hostile.

Even if the aircraft was tracked in radar by the military, that in itself is not sufficient for scrambling jets. Usually, the ATC will inform the authorities about any possible deviation; It is unlikely that the military would have real time details of aircraft routes. Note that it was not possible in this case (the aircraft transponder had gone silent before deviating from path). Also, there can be multiple reasons for loss of communications (usually equipment failure), and one does not immediately conclude that the aircraft has been hijacked.

Scrambling jets is usually the last resort and are sent to shoot the non-responsive aircraft. You don't shoot a civil aircraft with hundreds of passengers just because a microphone stopped working. The ATC must confirm that it had deviated from path and then the aircraft must be deemed a credible threat.

While the procedures for scrambling military aircraft are usually classified, it can be assumed that they are different in case of US (and Europe) and rest of the world. It takes a lot of resources to keep aircraft and pilots ready to intercept aircraft, which not all countries have (or even require most of the time).