score:7
According to this forum thread in 2011, someone actually called Allegiant over this:
I called back in the middle of Jan. and was told the middle of March.
Upvote:2
Airlines add dates based on their own preferences. Some add dates in advance and open bookings for so many days in the future. Some add dates every week or every month. Some add dates based on season, such as all summer dates at one time.
Upvote:7
You don't indicate where you are proposing to fly from/to so a general answer:
When will you announce new dates or routes?
Canβt find your favorite route on the flight calendar? Some flight routes are seasonal. Click here to view the interactive route map.
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That is, there may be no flights on your route after August 15, 2017, at least not until the new season. Seasonal routes can be seen here (supposedly).