2020 was tough for the aviation world but 2021 will offer many new routes. See thread to find your local airport and see what new flights and airlines could serve your airport in 2021 (subject to change):

New routes at London Heathrow in 2021:
American Airlines - Boston, Seattle
Blue Air - Cluj
British Airways - Bermuda, Orlando
Delta Airlines - Seattle
Virgin Atlantic - Orlando, San Juan, St Vincent
Vistara - Mumbai

New routes at London Gatwick in 2021 (1/2):
Aegean Airlines - Corfu, Heraklion, Santorini
British Airways - Accra, Doha, Islamabad, Manchester
Corendon Airlines - Antalya, Dalaman, Heraklion, Rhodes
easyJet - Aberdeen, Bilbao, Cagliari, Enfidha
FlyOne - Chisinau

New routes at London Gatwick in 2021 (2/2):
Nouvelair - Tunis
Royal Air Maroc - Agadir, Marrakech
SunExpress - Antalya
Wizz Air - Malaga

New routes at Manchester in 2021 (1/2):
airBaltic - Riga
Blue Islands - Southampton
British Airways - London Gatwick
Corendon Airlines - Dalaman
easyJet - Enfidha, Ibiza, Kos
Jet2 - Jersey, Kalamata, Mykonos, Mytilene, Santorini
Loganair - Newquay
Nouvelair - Monastir

New routes at Manchester in 2021 (2/2):
Royal Air Maroc - Agadir
Ryanair - Bucharest
SunExpress - Antalya
Turkish Airlines - Antalya, Dalaman

New routes at London Stansted in 2021:
Jet2 - Jersey, Mykonos, Mytilene, Preveza, Santorini
Ryanair - Oradea
TUI - Boa Vista, Sharm El Sheikh

New routes at London Luton in 2021:
Blue Air - Cluj
easyJet - Marrakech, Zakynthos
Wizz Air - Alicante, Dalaman

New routes at Edinburgh in 2021:
BA CityFlyer - Southampton
easyJet - Gibraltar
Loganair - Jersey, Newquay

New routes at Birmingham in 2021:
Jet2 - Amsterdam, Jersey, Nice, Preveza, Santorini
TUI - Banjul

New routes at Bristol in 2021 (1/2):
easyJet - Kos, Preveza
Jet2 - Almeria, Antalya, Corfu, Dalaman, Fuerteventura, Faro, Geneva, Girona, Gran Canaria, Heraklion, Ibiza, Izmir, Kalamata, Kefalonia, Kos, Lanzarote, Menorca, Mytilene, Naples, Palma, Preveza, Reus, Rhodes (cont...)

New routes at Bristol in 2021 (2/2):
Jet2 - Salzburg, Santorini, Skiathos, Tenerife, Thessaloniki, Verona, Zakynthos
TUI - Sharm El Sheikh

New routes at Glasgow in 2021:
easyJet - Pula
Loganair - Exeter, Newquay

New routes at Belfast International in 2021:
TUI - Kos

New routes at Newcastle in 2021:
Jet2 - Geneva, Jersey, Kefalonia, Salzburg, Santorini, Skiathos
Loganair - Newquay
TUI - Hurghada, Salzburg, Skiathos, Verona

New routes at London City in 2021:
BA CityFlyer - San Sebastián

New routes at East Midlands in 2021:
Jet2 - Jersey, Skiathos
TUI - Sharm El Sheikh

New routes at Leeds/Bradford in 2021:
Jet2 - Santorini, Skiathos

New routes at Aberdeen in 2021:
easyJet - London Gatwick
Loganair - Newquay (via Newcastle), Teesside

New routes at Belfast City in 2021:
Eastern Airways - Cardiff
Loganair - Teesside

New routes at Southampton in 2021:
BA CityFlyer - Bergerac, Berlin, Edinburgh, Faro, Florence, Ibiza, Limoges, Malaga, Mykonos, Nice, Palma
Blue Islands - Dublin, Manchester
Eastern Airways - Dublin

New routes at Jersey in 2021:
Jet2 - Birmingham, East Midlands, London Stansted, Manchester, Newcastle
Loganair - Edinburgh, Teesside

New routes at Cardiff in 2021:
Eastern Airways - Belfast City
TUI - Sharm El Sheikh
Wizz Air - Alicante, Corfu, Faro, Heraklion, Lanzarote, Larnaca, Palma, Sharm El Sheikh, Tenerife

New routes at Doncaster/Sheffield in 2021:
TUI - Boa Vista, Hurghada, Sharm El Sheikh
Wizz Air - Bourgas, Dalaman, Heraklion, Palma

New routes at Exeter in 2021:
Loganair - Glasgow