I am due to return to work after being off 10 weeks, using short term disability. I am not able to return to my position as I cannot travel by air.

Air travel has been deemed an essential function of that role. I have been told by HR that I must continue short term disability until i find another position with the company. First question: Am I obligated to remain on disability even though the only "disability" is my air travel restriction? Second question: I was told I must apply for jobs just as any other candidate, and that if I'm not chosen for a job by the time short term disability runs out, I must go on long term disability. Is this correct? Is my employer obligated to reassign me to another position, or must I go through the hiring process as though I am an outside applicant?