The estimates from executives and analysts I've read predict it will take 2-3 years to get back to previous travel levels. Assuming UAL matches the industrial trends, the company will be back to needing the current level of pilots in 2-3 years if the predictions hold true. The future is unpredictable, but considering mandatory retirements hopefully all UAL pilots will be back on the property (assuming a furlough) within a reasonable amount of time.