When it comes to pricing flights to fill, airlines rely on mysterious computer-based algorithms that can mean the person who just elbowed you off the armrest paid far more or less than you did. Fortunately, fliers have a few web-based tools at hand, too.

Online flight aggregators (which send you to the airline for booking) and online travel agents (which sell tickets directly) can quickly ferret out the lowest-priced flight — as can live travel agents, who have their own technological means. At the aggregator Skyscanner.com, users can search for flights from their home airport to "everywhere," handy for those with vacation dates but no clear destination. Airfare price alerts are another powerful way to uncover deals; an array of websites such as momondo.com, kayak.com and Google Flights (google.com/flights) track airline price shifts and send notes when prices drop.

Among the web-based services, Google Flights is my go-to, primarily because it is easy — and inspiring — to use. To quickly see how a change in dates alters airfares, simply click the arrows in the date field. The site also predicts the best time to buy based on historical pricing data. And (here comes the inspiring part), click on the "explore destinations" key and a range of options pop up on a map (Seattle for $177 and Denver for a mere $57).

The key for bargain hunters is to check with several sites before buying. A Consumer Reports study found different prices for the same flight on various online travel agents and fare aggregators. My own experience reflects that: Momondo recently uncovered a better deal than Google Flights.

Kerri Westenberg