Looks like that flight maxed out at 38,000 feet: http://flightaware.com/live/flight/U...319Z/KORD/KSFO

I have seen on flightaware where a T7 will fly upwards of 40K feet, but only on ferry flights.

The only commercial planes that I've seen (or been on / heard about - gotta love channel 9) at or above 40,000 feet are:
- 757 (been on a couple of UAL flights at 40K)
- 747 (been on at least one UAL flight that hit 41K)
- 737NG (heard ATC clearing Southwest flights to 40K)

The max cruise altitude is determined by a few factors, including engine power (I'd bet the T7 has the power to climb that high, unlike a CRJ200), but also the airframe's ability to withstand the dive back to 10,000 in the event of the loss of cabin pressure. The FAA has set a strict time for how quickly a plane must be back at or below 10,000 feet and that time (which is something like 10 minutes, but don't quote me on that) determines how steep (and fast) the dive must be. I've heard the 747 has the highest operating ceiling (43K feet) of any commercial aircraft.

BTW, there are lots of business jets that cruise up to 45K feet (if not higher).