Hi eilonwy
My son was about 6 when he became flight obsessed. Some things we did:
~ measured out the size of a 747 on our (quiet) street and compared with some other planes he was interested in
~ found a computer flight simulator game for kids on ebay called kids pilot by edmark I think and that was a hit for a while until he wanted something more sophisticated - it would definitely be suitable for a 5 y/o
~ found a
greeat book
which had a poster of a flight panel, cardboard pilot's wings etc.
~ made our own flight control panel out of a cardboard box and various things (straws, buttons, bulldog clips etc), made tickets and went on flights
~ made more lego planes than I thought humanly possible

~ found an unused DK kit about flight at a garage sale - it was great, had models of different planes and I can't remember what else
~ made a flight timeline for around his room from pictures he drew or we printed out, or cut from magazines (hung these on a string from cup hooks in the ceiling so that any 3d versions he made didn't get crushed against the wall)
~ watched a videos about flight including "leonardo: a dream of flight", "Dawn of the Jet Age" and "the magic of flight" (which I think was our favourite but I can't remember for sure)
~ read the book and watched the magic school bus video about flight
~ did science experiments to demonstrate wind resistance, the Bernoulli effect etc -found most of these in lesson plans I googled
~ national geographic did a great edition on flight to celebrate the 100 yr anniversary of the wright brothers flight (dec 2003) and they had a great poster of 'significant' planes in the history of flight - you might see if ebay has a copy
~ we toured our little local airport, went to an airshow and a flight museum, and went to the big airport to watch planes.
~ went to watch a model plane flying club exhibition (they fly models of airplanes which are about 4 feet long - our local club does this about once a month in the summer)
~ we added to the collection of little planes he has (ie tinker toy size) whenever we could and he made his own flight museum and gave tours - they were a riot.
~ we had flight competitions with planes made from paper, cardboard, balsa wood and foam (the cheapo $ store version or ones we made from meat trays) on our street - the whole family chose a plane and we all tried to fly them to see which would go furthest
~ we made paper helicopters, chased hot air balloons to their landing pads,
~ I found this great UFO "toy It is just a huge very thin plastic garbage bag, open at both ends. You tie one end off, fill it with air and tie the second end off with a long string. When it heats up in the sun it will levitate/fly. The kids LOVED it. Unfortunately it isn't very durable and so it only lasted a couple of days before the amount of scotch tape made it too heavy to fly

~ I googled "airplanes for kids" for my son not too long ago and this site came up. I have not checked out all the links but it might be helpful.
airplanes for kids. There are tons of things. Also try googling "lesson plans flight" for crafts and activities to try.
Ok - that was a lot of

. Hope you can use some of this.
Karen