The following is a list of links that may be useful for those wishing to participate in O.T.A. events.
This is by no means an exhaustive list so feel free to add any accordingly.
(Please ensure that information isn't repeated though to prevent confusion.)
Note that many O.T.A. events run at particular times or dates of the year so mark your calendars accordingly.
S.O.T.A. - Summits On The Air - https://www.sota.org.uk/
P.O.T.A. - Parks On The Air - https://docs.pota.app/
I.O.T.A. - Islands On The Air - https://www.iota-world.org/
Y.O.T.O. - Youngsters On The Air - https://www.ham-yota.com/
B.O.T.A. - Bunkers On The Air - https://bunkersontheair.org/site/
R.O.T.A. - Railways On The Air - https://rota.barac.org.uk/
A.O.T.A. - Airfields On The Air - https://www.rafars.org/rafaota/
For events such as 'Mills On The Air' these are usually run independently by various clubs so worth a search for M.O.T.A. and club sites.
Not forgetting that there are some other popular events not specifically entitled "On The Air" such as :
-I.L.L.W. - International Lighthouse Lightship Weekend - https://illw.net/
W.W.F.F. - World Wide Flora & Fauna - https://wwff.co/
There are many other events of a similar vein taking part in 'On-Air' events so worth a search and if you find anything useful or maybe interesting to others then why not add to this posting with your links or information.
I personally haven't taken part in any of these kind of events before but looking forward to having a go and marking my calendar for 2025. Some have rolled out these events so that not only SSB/CW contacts can be made but also digital modes such as FT8 opening the doors to even QRP or limited Foundation stations. Check sites for operating modes accordingly.
Note that some of these events are taken very seriously with scoreboards and/or certificates available, some are mostly for the fun of radio (my favourite pastime) and of course the feel good factor that can arise from activities such as Y.O.T.A. seeing youngsters using Amateur Radio for the first time.
Something for everyone really then.
All the best,
Victor