Google Flights
One of the best spots to check for cheap flights (notably excluding SouthWest) is on Google Flights. Generally, you'll find cheaper options booked a month or more out, with options on some carriers being cheapest as soon as they are available to book (i.e. SouthWest).
Enter Departure City/Cities/Airports, & Consider Looking for 1 Way Pricing 1st; The More Cities You Enter, the Lower the Prices You Might Find
As soon as you go there and enter a departure city, before doing anything further, some decent options may pop up:
Image courtesy https://www.google.com/travel/flights
To locate cheap spots, you may want to check the options that are easy to get to. For instance, in Hampton Roads, VA, you might check the options from PHF (Newport News), Richmond (RIC), & Norfolk (ORF) instead of just your closest airport.
Image courtesy https://www.google.com/travel/flights
The more options you add, especially as you get into bigger cities, the cheaper the flights will be. Also, you may want to check based on 1 ways, though sometimes round trips can be heavily discounted vs the same flights booked one way each (in some cases less than either 1 way). Here's a search 1 way where I've added Washington to the mix:
Image courtesy https://www.google.com/travel/flights
If adding Washington and departing from a location like SE VA, consider other big airports within the perimeter of you. DC (IAD & DCA) is around 3 hours away from me in SE VA, so it's not a bad idea to consider departure from Raleigh. Even Baltimore is within reach.
Flexible To Field Options
If you're looking for domestic flights, you might even want to see where you can go by typing in "United States" in the "Where to?" field:
Image courtesy https://www.google.com/travel/flights
From there, you'll see a number of possibilities that you can scroll down on for the cheapest flights on a particular date:
You can search by state, country, continent, etc. You can even input "anywhere".
Here's an example to Europe under $200 1 way:
Want to go to Central America for under $100? Why not?
Narrow by Price
After clicking "All Filters" you can also narrow down to the cheapest options:
Image courtesy https://www.google.com/travel/flights
Image courtesy https://www.google.com/travel/flights
Image courtesy https://www.google.com/travel/flights
Removing DC, there are only a few options on that date for less than $50, so by upping the minimum threshold to $100, you'll see many more options:
Image courtesy https://www.google.com/travel/flights
Look Out for Google Pop Ups
Look out for the helpful pop-ups that Google shows at times as well, like this one, though they often don't include the carry-on bag in that cost:
Image courtesy https://www.google.com/travel/flights
Explore Using the Date Grid & Price Graph
The date grid feature and the price graph are excellent Google Flights features as well, with the date grid one being best for those looking exclusively at a 1 week window,
The price graph better for those with more flexibility:
Flexible Dates
Another great option with Google flights is the "flexible dates" option:
That's how I found this round trip for $217
In other countries, sometimes the dollar can go a lot further than it can in the US (& vice versa).
Lookup up to $100 through the US with flexible dates up to 6 months, you can find options like this example:
Avoid Phantom Options On the Left with No Pricing
If there's no pricing visible on the left for a particular city when you have price filters, it's likely that by zooming in, you'll find that it's not exactly a match.
Play with the Map Visually To Expose Hidden Options You Won't Find Otherwise Due to a Persistent Google Maps Glitch
If I zoom far out on a map, I'll see less viable options than if I play around with the map using the Zoom tool, both directly on the map & on the left. In the below example, I'll show you how 6 available city options under $50 becomes 11 options by playing around with the map without adjusting any part of the search criteria besides your view of the map.
Here is a search without zooming in for the next 6 months from SE VA under $50:
I only see 6 cities priced out on the left, & even fewer cities priced out directly on the map. Zooming on the map can yield even more and the blue dots will sometimes show pricing when zoomed in since they are eligible cities within the criteria including pricing. With the above map, there are 8 options on the left, though 2 of them don't include pricing, and when you zoom in, they still don't show any pricing and are no longer on the left.
Even if you scroll to the bottom of the search at the left for the vertical view which includes the airline, it only shows 6 viable city options. By zooming in on the exact same search, you'll get a lot more options. Zoom in on the NE to get Cincinatti & Hartford in this example:
Go further in & it opens up Syracuse & Westchester County:
Akron also opens up:
Charleston, Tampa, & Orlando become visible:
Tampa, Ft. Lauderdale, & Miami open up:
This same rule applies when pricing
Consider Hiding Separate Tickets (Or Not)
While you'll sometimes find cheaper options by using the default option of including separate tickets, you may want to eliminate that option. Separate tickets means that if your first flight is delayed, you might miss that 2nd flight from another airline with poor recourse to rebook without hefty charges since you'll often be treated as though you missed your flight. You can weed these out by going to "all filters" & using the filter for it at the bottom of the additional filters:
That said, in some cases, you could be losing out on deep discounts when there was actually a long time between flights:
Set Price Alerts
One option as well with Google Flights is that you can set an alert for many itineraries with the "track prices" feature. It won't work though for some searches like options to "Europe" on the map view for 6 months out, sadly.
Most images courtesy https://www.google.com/travel/flights