TMZ has learned the plan to get Britney into UCLA Medical Center had been hatched for days -- it was aborted last night, but executed just minutes ago. And we're told the plan was so intricate the FAA had cleared airspace in route to the hospital.

Back at her house, Britney's psychiatrist told her she was going to the hospital. Her response was, "Is something wrong?" She was not resistant. She made hot chocolate and waited before paramedics arrived and placed her on a gurney.

We're told the psychiatrist felt her condition had deteriorated. Britney had not slept since Saturday -- a day and half longer than she stayed up in recent memory.