This flight flightaware.com/live/flight/EXU151 is registered to Kyrgyzstan and inbound from Beirut. Any thoughts? Is the registration correct or is EXU a company code?
Probably a company code.
Kyrgyzstani registrations don’t have a letter after the EX.
There is a GV based in Beirut, but for the life of me I can’t remember the registration or operator. Unless I’m confusing my aircraft it is an ex-Brunei airplane.
John
As of last June: EXU is the ICAO company id for Executive Airlines, S.L.; in Spain. Call Sign “Sacir”.
Connection to Kyrgyzstan 
I’m stumped.
There’s no connection, our code just looks for country codes before operator codes.
flightaware.com/live/flight/EXU2313 Seems they’ve used a Gulf IV in the past.
Only biz jets in Kyrgyzstan under their registration are;
UP-A2001 Airbus A320CJ
UP-C8501 Challenger 850
UP-C8502 Challenger 850
UP-CS401 Cessna 650 Citation VI
UP-P1001 Beech 390 Premier I
Could be a Nxxx or VP-xxx number???
EX-is the PREFIX for Kyrgyzstan.
The SACIR (EXU) Gulfstream is any one of the follwing: see
…mostly operating out of Barcelona.
remember all the fun way back with Congolese tailnumbers that were in fact Far91/135 flights (e.g TN92AE). Dysfunctional computer logic. 
IN
I had contacted Bob Wembley the Gulfstream Historian.
Though the answer is already above, EXU is Executive Airlines of Spain.
Their newer Gulfstream G550 s/n 5151 is EXU151.
Aircraft is owned by Royal Scott Leasing and operated by Executive Airlines.
photo by Fernando Olmeda/Iberian spotters