Something that's grinding my gears about the media reports I've been hearing:
"Air Asia jet crashed after being denied permission to climb to avoid weather by ATC"
ATC can only know what a pilot tells us. If the captain feels the weather ahead poses such a significant threat to his/her aircraft, he/she should have say in the first transmission "need immediate left turn 120 degrees and climb to FL380 due weather". If the ATC response was not to their satisfaction, say the magic words and do it anyway. If you are in conflict with another aircraft, it's my job to get it out of your way in those situations. You are my number 1 priority and nobody is getting in your way.
The aircraft was approaching handover to another center from what I've read. The next sector is expecting that aircraft at FL320, and is planning their separations and crosses based on that fact. It varies from place to place but normally if the climb is being initiated within 10 mins of an FIR boundary, I have to pick up the phone and get permission for a climb BEFORE giving it to the aircraft.
Also, if the aircraft is crossing an FIR boundary, it needs to meet certain conditions for silent handover, IE to be handed to the next sector e.g. 10 nm at boundary behind traffic ahead if same speed or slower, 20 nm if faster. Not to mention coming at the next sector off route. Also, in this instance, you would warn the next sector about the weather reported so they will expect subsequent aircraft off route and warn any aircraft they are sending your way. Anything that does not meet silent handover criteria must be manually co-ordinated over the phone and approved by the giving and receiving sectors.
That little rant is just to give you an idea of some of the criteria that we need to meet to give climbs or re-routes in non emergency situations, and how important it is that the magic words are used if you aren't getting what you need