I work for a Fortune 50 (not tech) company...
<6: Y (but not allowed to book basic economy)
>6: J allowed by policy, but you might get a weird look if you booked it on, say, BOS-SFO... It’s really meant more for international travel. If I was flying DFW-LHR, it would be J all the way no questions asked.
There’s also a “weird” provision where if you’re flying to certain “high-risk” countries, you can fly J no matter the flight length.