airline reservations

No one has that crystal ball. Since COVID the airlines have been somewhat chaotic.
Use Google Flights to track prices by setting up alerts. Purchase tickets directly from the airlines, not third party sites, however.
When you find a price that seems reasonable, buy it and don't look back.
Safe travels!

Others will have better advice, but I've consistently done well looking at prices a year in advance (when they're first available) and using skyscanner/googleflights for updates. I've always come out ahead booking nearly a year before the trip. For example our summer trip to Scotland was booked in July 2022. The cost now is about $1,000 more for premium economy.

edit: and what Pat said

You can do a SEARCH for this as it's brought up often. But we've always had the best price on opening day which is 330 days from your return flight back home.

The past 3 trips to Europe we booked at our 330 day mark and checked back a few times later and the prices were anywhere from $300 to $700 more.

We booked our flights for December 2023 in Feb at our 330 day mark - into Munich and out of Amsterdam (we always book MULTI CITY to Europe) and we paid $920 for Premium Select seats - now those seats are $2600 and Coach is $1400.

We are going to Europe again in April 2024 and Sept 2024 and I plan to book those flights at our 330 day mark.

What holds true today may change tomorrow. That said I follow the advice given above and book as soon as they become available after carefully watching prices. Doing that I have saved big. My airfare for a trip now 6 months out is $3000 more per ticket (business/first class), however booking that far in advance is not without disadvantages.

The trend recently has been that prices have been increasing steadily. Sometimes there are sales, but no one can predict when and if. Demand seems quite high at the moment.

We bought our flights for this May during the Black Friday weekend in last November. Fares were very good and we upgraded to extra legroom seats as they were available. So far, there haven't been any flight changes. Last year, we did the same thing but scheduling within the entire airline industry was crazy. Our fights changed multiple times in the five months before the trip. We were able to reschedule each time and everything turned out fine.

I think booking early is probably more important if you're looking for premium seats of some type; I fly regular coach. I've noticed in the past that the spread between the most convenient itineraries (fewest changes, reasonable layovers) and worse options tends to expand significantly as the travel date approaches, so I think folks traveling to not-so-easy destinations who are going to insist on a good routing would also be well advised to make a relatively early purchase.

I'm less convinced it will continue to pay off greatly for regular-coach travelers to buy at the 330-day mark. Right now, we're in a period of escalating airfares for several reasons, including staffing issues, fuels costs and pent-up demand (the latter due to a huge improvement in the COVID situation). Naturally, people who took a chance and bought tickets early in 2022 for travel late last year or early in 2023 did quite well. I'm not at all sure that pattern will continue.

Super-early purchase carries with it the risk that travel plans/priorities will change. I'd rather have the ticket money in my bank account than in the form of an airline credit. (No, I don't buy travel insurance to cover losses I could absorb.)