JAL (Japan Airiines) offers free tours of their maintenance facilities and their Sky Museum at Haneda Airport in Tokyo. You can see planes in a huge hangar being serviced.

You have to make reservations at their website, but everything is in Japanese. They have four 90-min. tours almost daily, but only in Japanese. You should reserve weeks or months in advance because tours get booked up quickly. However, when people cancel their reservations, tours may open up. You have to keep checking. Children must be at least elementary school age. Shin Seibijo Station on the Haneda Monorail. JAL's maintenance hangar is a 10-15 min. walk from Shin Seibijo Station on the Haneda Monorail running from JR Hamamatsucho. http://www.jal.co.jp/kengaku/tour/