system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] Why was Thor briefly unable to call Mjolnir to him after falling out the helicarrier in The Avengers?
gpt
[SPOILERS!]

It's possible that he hadn't properly called it yet out of hesitation.  He began raise his hand of habit, but stopped just short of actually calling for Mjolnir.

Thor had just found out that Loki orchestrated a very effective attack on Earth's forces.  He started by making himself seen infront of a large crowd, letting himself get captured so he could be in the right place at the right time.  His troops flew unchallenged to the helicarrier, nearly destroying it and everyone onboard.  Hulk was unleashed, and everyone else was busy trying to keep the helicarrier from crashing.  Thor was tricked by his brother yet again, trapped in a cage and forced to watch helplessly as Agent Coleson was mortally wounded trying to stop Loki.  He was then dropped from high altitude in the same cage that had held his brother only minutes before.

Thor was questioning his own worthiness.  He screwed up bad, and everyone else was paying the price.  Even if he wasn't worthy in his own eyes, he needed to make things right the best he could.  When he finally did call to Mjolnir, it came.  In his father's eyes, he was still worthy.