Ah well, it seems that those days will never return.
I still remember when I was fortunate enough to failover to a concorde when our 747 was grounded ~20 years ago and got to visit the cockpit in flight. There was a seam between two portions of the cockpit (a little less than an inch wide) that only existed when the plane was supersonic, and it closed tight when not.
Wouldn't have been able to scare a kid into thinking they could get their hand stuck in there if the plane was still on the ground ;)
Of course whether or not in-flight cockpit visits were still allowed, that particular experience wouldn't happen anymore.
Apparently in the 1960s to early 1970s, you could buy your ticket on the plane. (I wasn't around to have experienced that.)
I wasn't a kid, but I got to hang out in the cockpit for a good-half hour on a cross-province Air Canada flight long after it was illegal in USA airspace (1990s). The amazing thing, apart from the scenery, was that you could see dozens of other jets in various headings and altitudes.
Then again, I also remember when kids were routinely let into the cockpit, either before takeoff or while cruising.
Air travel used to be almost fun.