[UPDATE – see this link]
Yesterday this ARJ21 was spotted in Vienna. The aircraft is B-1110L and apparently doing test flights outside China.  The aircraft has been doing tests in the UK and has also been spotted in Oslo. From Vienna it is reported the aircraft was headed to Ankara.
Prior to the EU flights we noted this report from January 24th. This was followed by cold tests on January 27th. In early April B-1110L was in Windsor, Canada for more tests.
The ARJ program is running very late (initial deliveries were planned for 2007). That said, it appears to be coming along or COMAC would not risk flying it outside China as it has been. There is scant information on the aircraft’s performance or economics. We suspect the aircraft is overweight and therefore has relatively inefficient economics. But confidence in taking the aircraft in such long range tests indicates its systems are robust enough and the aircraft as a whole is working.
COMAC has plans to deliver the aircraft this year to launch customer Chengdu Airlines. Getting CAAC certification is crucial for COMAC. The US FAA has been conducting a “shadow certification process” alongside CAAC. The FAA has said it would not start working on the C919 until it completes the certification of the ARJ. Since it may take the FAA up to two years after the CAAC certification to complete its work, the pressure is on. Although after 11 years, customers may be exhausted. No western OEM could expect to deliver an aircraft to a customer this late.
Uncanny similarities with the Fokker 100
http://en.wikipedia.org/wiki/Fokker_100#Specifications
unfortunately it is worse: http://en.wikipedia.org/wiki/McDonnell_Douglas_MD-80/MD-90