Jet test pilot wore gorilla suit

[snopes]

Comment: I was wondering if there was any truth to the rumor that a test
pilot wore a gorilla suit either as a security measure or a joke during
testing of the first US jet airframe. I have found the following three
stories online at different forum sites.

The fable is reminiscent of the P-59's saga: the story of the first
military jet aircraft to fly in the United States—an aircraft that
apparently no one could see. The date was 1942; the location was Muroc
Army Air Field (today Edwards Air Force Base). Whenever it was on the
ground, the P-59 was fitted with a fake propeller for the sake of secrecy.
Unfortunately for secrecy, at the local watering hole, test pilots mixed
with P-38 pilots stationed nearby. After slugging down a few drinks, the
test pilots bragged about flying a propellerless aircraft and were
immediately labeled as liars by the P-38 crowd—fighting words for sure.
Subsequently, test-pilot Jack Woolams decided to put them in their place,
not with his fists but with something far more effective. 2
He rented a gorilla suit and took off wearing it along with a big cigar
protruding from his mouth and a derby hat on his head. Once airborne, he
found a lone P-38 pilot, pulled alongside, giving the P-38 pilot a clear
view of the jet and gorilla suit, then waved, much to the shock of his
intended target. The next day when queried at the local watering hole, not
a single P-38 pilot had seen an "escaped gorilla" or knew anything about
it. The explanation: why of course, it must be that P-38 pilots could only
see what they believed was possible. Yeah, right. Apparently, the P-38
pilots never again questioned the possibility of propellerless aircraft,
let alone the honesty of test pilots.

Although the events are not even a century old, already there are more
than one version of the Jack Woolams tale. All are slightly different. One
version relates that there were multiple sightings of the gorilla-piloted
jet and that the base psychiatrist talked several P-38 pilots out of
believing what they saw.3 Who knows? The fact is, that even if someone
sees and believes a phenomenon, it doesn't mean they will honestly talk
about it. And if they do, it doesn't mean that the details will be
perfectly remembered in the historical record—especially if there isn't
one.

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During initial flight testing of the P-59, Bell personnel could be
distinguished by their trademark black derby hats. Although the airspace
around Muroc Dry Lake was restricted, P-38 pilots from a nearby Army field
would occasionally invade the area to see what was going on at the
"secret" base. On one flight, Bell test-pilot Jack Woolams spotted one of
the snoopers and pulled on a rubber gorilla mask he had brought along, put
on his derby, stuck a big cigar in his mouth, then let the P-38 pull
alongside. He glared back at the stunned pilot, who quickly broke off.

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Belling the Ape

During initial flight testing of P-59 at George AFB (then Hawes Field) CA,
Bell personnel could be distinguished by their trademark black derby hats.
Although the airspace around George and Muroc Dry Lake was restricted,
P-38 pilots from a nearby Army field would occasionally invade the area to
see what was going on at the "secret" base.

On one low-speed flight, Bell test-pilot Jack Woolams spotted one of
the snoopers approaching, and was ready for him. He pulled on a rubber
gorilla mask he had brought along, put on his derby, and stuck a big cigar
in his mouth, then let the P-38 pull alongside his jet. He glared back at
the stunned pilot, who quickly broke off and headed for home.

There was no official follow-up to this episode, but it was the source
of much hilarity among Bell workers who speculated about the story being
told that night at some Officers Club of a propellerless plane being flown
by a cigar-smoking gorilla wearing a derby hat! It might well have been
the forerunner of the flying saucer tales a decade later. (— K O Eckland)

[DrRocket]

Test pilots, by their nature, tend to be larger than life types. Woolams was known for his derby hat and cigar.
Here's another page on the history of the plane, and it does mention an encounter with P38's including the hat and cigar, but no mention of the gorilla mask. I have a suspicion that take on the story is apocryphal. On that page, you can see a photo of the plane with the fake propeller attached. Back then, people expected to see propellers.