Photos of the Janet 737s at Paine Field
http://microvoltradio.com/janet.htm

reminded me to track them by their Callsign as they use the ex-Air Force last 3 of the serial as their trip number when on positioning flights. The last 3 are clearly visible on the cockpit of the fleet.

for completeness, the T-43A fleet

282 N5175U ex 72-0282
283 (72-0283) stored at Davis Monthan
284 N5294E ex 72-0284
285 N5176Y ex 72-0285
286 N5177C ex 72-0286
287 N5294M ex 72-0287
288 72-0288 'RA' still active and puts in airshow appearances regularly
289 doesn't exist, the CT-43A that crashed nr Dubrovnik was 73-1147 from memory

290 N4529W B737 not sure why they chose '290'

I wonder if the ex-Janet 737s N4508W, N4510W and N4515W had fleet numbers assigned. I guess a closer inspection of old photos will show this.