The cheapest flights to Serbia recently found by momondo users are £9 with Ryanair, £30 with Air Serbia, and £33 with easyJet.
Serbia has reopened its borders. Incoming travelers will be provided on arrival with instructions on preventing the spread of coronavirus. If you have booked, or are looking to book, flights between Serbia and another country, you should be aware that changes and cancellations are possible as flights restart. Foreign nationals who have a temporary stay authorisation in Serbia which expired after March 15, 2020 will be allowed to enter the Republic of Serbia until July 1, 2020. They can legally submit a request for extension of their temporary stay within 30 days from their arrival in Serbia. If you are planning to travel to Serbia at this time, it is recommended that you stay up to date on current restrictions and follow proper safety measures while in public.