I think the general public would be very surprised if they got up close to any 15 year old jet. Evidence of historical leaks are commonplace. It doesn't necessarily mean the aircraft is unsafe.
This. I recall walking around under the B-70 at the USAF museum before they cleaned it up, looking up at the film of hydraulic fluid and rubber dust that coated it, and thinking "Boy, this looks like a real airplane!"
(The exhibits there are usually just a little
too clean.)
Yes. On a C or D check, we would park the arriving aircraft and powerwash the entire "works" of the aircraft after opening all access panels to the mechanicals. Then let it drip dry overnight. These were regularly serviced aircraft from a major airline, and skydrol, grease, oil, fuel, bluewater, etc was everywhere.
You can't inspect an aircraft covered in goo.