Low-cost carrier Wizz Air is to launch a new service from Belgrade to Luton, according to ABTN's sister website BusinessTraveller.com.
The Hungarian airline will also put on flights from Riga to the London airport, and from Wroclaw to Cork and Doncaster/Sheffield.
A thrice-weekly service between Luton and Belgrade will start on July 24.
BA currently serves the Serbian capital with flights from London Heathrow, as does national carrier Jat Airways.
Ahead of the launch of the Belgrade service Wizz Air will also commence flights from Doncaster/Sheffield to Wroclaw on March 12, and from Cork to the Polish city on March 14. The carrier will also start flying from Luton to Riga on March 30. The Latvian capital is currently served by Ryanair from Stansted, and Air Baltic from Gatwick.
Meanwhile, Irish carrier Aer Arann is to launch several new routes including flights from the City of Derry airport to Manchester and Edinburgh.
The airline will commence a seven-times weekly service from Derry to Manchester on May 20, along with six flights per week from the Northern Irish city to Edinburgh starting on the same day.
Aer Arann is also reintroducing its link between Kerry and Manchester "due to popular demand", with a four-times weekly service also commencing on May 20.
The carrier is also making changes to existing routes, with its City of Derry-Dublin service moving to an earlier departure time of 0740 (arriving at 0830), and its flights from Donegal to Glasgow switching from Prestwick airport to the more central Glasgow International airport from March 28.
The new routes follow Aer Arann's recent franchise agreement with Aer Lingus, whereby Aer Arann will operate 12 routes from Dublin and Cork to the UK under the brand name "Aer Lingus Regional".