can I make reservations to visit the cockpit Sunday May 16 in the morning?

I would check with the museum but as of recent times they were not taking reservations at all, it was first come first serve. I went on a busy weekend and arrived at 11:00 and they were out of reservations already for the rest of the day.

https://www.evergreenmuseum.org/museum-by-reservation You can reserve general admission and personal tours, the cockpit tours sell out as Edwin mentioned. Give the museum a call.