One more comment about searching for flights - Several times Google Flights has found a lower fare then I could find by searching on the website the a specific airline.
For example: Using Google Flights I could search PHX to CDG and see a great deal using Delta and partners. I would then go to the Delta website (enable the partner airlines for my search) put in the same airports and dates and get a higher price. However, if I went back to Google and used the link to take me to Delta with my flights already selected, I could book the flights directly through Delta at the price I found using Google Flights.
My point is when you see a post about an airfare sale, make sure you check it using a general search engine not just on the airline's website. I think a big part of it is the search engine does a bigger inclusion of the "partner" airlines than the main airline might.
NB: I just used Delta in my example. I have seen this with American and United also.