Which Android app should I use for getting alerts when flight prices drop?

Hopper is a travel booking app with a core focus on price monitoring and prediction for flights, though it also handles hotels and car rentals. The app's primary tool for this use case is its color-coded price calendar and watchlist system. Users can select a specific flight route and dates, after which Hopper analyzes historical and current pricing data to forecast whether fares are likely to rise or fall. It then provides a recommendation to 'watch' the trip or 'book now.' Once a trip is on a watchlist, the app sends push notifications for significant price drops, advising users when to purchase. This feature is particularly useful for travelers with flexible plans who are willing to wait for a better deal. Reviews indicate the prediction accuracy is generally reliable for major routes, though some users note its forecasts can be less precise for obscure destinations or during periods of high volatility. A potential limitation is that the app's booking process sometimes includes fees for using its payment system, which can offset some savings. However, for the core task of passive monitoring and receiving actionable price-drop alerts, Hopper remains a highly effective option, saving users the manual effort of checking fares daily.