Boeing 737-500 Question

[Go4fun]

I was watching a show about air crashes involving this aircraft. They explained about what happened and how it was finally fixed.
But my question involves something I saw in 'Filler Shots'. As 737s were taxiing, taking off and landing I kept seeing a very tiny parachute attached to to top of tail fin by a short leash. Several different airlines and planes had this very tiny parachute. Some had it, some didn't.
QUESTION: What purpose would that serve?

[PR19_Kit]

I've seen that tiny chute on aircraft doing early trials, so maybe the ones you saw were taken at Boeing Field, or Everett or somewhere similar?

It's possibly to keep a wake data sensor in line behind the fin.

[Go4fun]

WThat sounds reasonable but why would planes in full airline livery be using them though?
"Well folks your tickets are half price because the FAA is doing some test during our flight today. And if we crash you get a full refund! Enjoy the ride".

[Captain Canada]

Wierd...hadn't noticed that before but now I have to go look !

[PR19_Kit]

WThat sounds reasonable but why would planes in full airline livery be using them though?
"Well folks your tickets are half price because the FAA is doing some test during our flight today. And if we crash you get a full refund! Enjoy the ride".

Because Boeing were carrying out the tests prior to delivery, and then they'd already be fully painted.