Airline prices are all governed by data analytics so there are no guidelines for the best price. There are deals but you cannot predict when those are available. The best you can do is know the prices, keep looking and jump on one when available. There are some sites that look for deals.
I will be traveling to SJPP October 1 and have found all the same issues you all have found. Even if the bus schedule comes out in a few weeks the timing probably means a night in Pamplona. I am resigned to hiring a taxi from the Pamplona airport 😔
I'm going in October and after checking the trains to Pamplona I chose to fly for 3 hours of extra sleep and 5€ more. I then booked a flight back from Santiago for 35€. I love trains but you can't beat that.
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