Its actually an A319, wet leased from Czech Republic’s CSA Czech Airline. I believe they are shortly getting a second one. The leasing airline supplies the crew too, when its wet-leased.
This is partly as a stop-gap solution till their whole 737 fleet is airworthy, which it isn't at the moment. They cannibalized some of their 737s for parts when their finances were in the red.

Here's the aircraft at CSIA:

http://img.planespotters.net/photo/6...Net_627759.jpg