There was sufficient aircraft for the operation because the original plan was scheduled for two drops per day. This was Monty's plan and was changed to only one drop per day by the commander of the First Allied Airbourne Army Lewis Brereton. Combined operations were still in their infancy so Brereton answered directly to SHAEF. No commander other than Ike could overrule him. On Gavin I have never in all the books I have read on Market Garden been lead to believe he had insufficient forces for his job. To be accusing Monty of insubordination is kind of ironic. The first person I can think of when hearing this word is Gavin. He didn't just fail to achieve his objectives on the day. He failed to follow orders and actually send any troops to the bridge. It's double irony because the British were finally early for a change so trying to blame them and the 1000's of illusory tanks that he had sole exclusive knowledge of sounds like excuses.