Complex sentence: On 8 November 2015, Estonian Air ceased all operations after the the European Commission declared the government fundings received by the airline as illegal which would have forced them to pay back over 85 million Euros.
Split into simpler sentences: On 8 November 2015, Estonian Air ceased all operations after the the European Commission declared the government fundings received by the airline as illegal. The airline would have been forced to pay back over 85 million Euros.