Here's a trick many points collectors miss: United Airlines flights don't have to be booked with United miles. Because United belongs to the Star Alliance, Air Canada's Aeroplan program can price and sell seats on the exact same planes — and sometimes for noticeably fewer points.

The catch is that both programs now use dynamic pricing, meaning award rates float with demand rather than following a fixed chart. A United flight might cost 32,500 MileagePlus miles one day and 60,000 the next, and Aeroplan's price for the same seat will not always match. Still, Aeroplan frequently undercuts United, especially on two fronts: short hops within North America, where Aeroplan's chart starts at just 6,000 points each way in economy for flights up to 500 miles, and transatlantic business class, where partner-operated awards start at 60,000 points one way for routes up to 4,000 miles (rising to 75,000, 90,000 or 110,000 points for longer distances).

Aeroplan has another practical advantage: transfer flexibility. American Express Membership Rewards points and Capital One miles move to Aeroplan at a 1:1 ratio, but neither transfers directly to United MileagePlus. Chase Ultimate Rewards and Bilt points also convert to Aeroplan at 1:1. So if your points live in Amex or Capital One accounts, Aeroplan may be the only sensible route to a United seat without an extra hop through another program.

Timing matters too. Transfer bonuses crop up regularly — for example, holders of the Air Canada Aeroplan Credit Card can currently get a 10% bonus when moving at least 50,000 Chase Ultimate Rewards points in a single transaction (capped at 25,000 bonus points per year, available through the end of December). A bonus like that can swing the math decisively in Aeroplan's favour.

Booking is straightforward: search on the Aeroplan website, tick "Book with Aeroplan points," pick your flights, and pay. Taxes and fees are charged in Canadian dollars — expect roughly CA$47 (about $34) in taxes on a typical award, plus a CA$39 (about $27) partner booking fee per ticket. Booking by phone adds a nonrefundable CA$30 (about $21) service fee, so stick to the website.

Two warnings before you commit. First, United doesn't release every award seat to partners, and prices differ between programs, so compare MileagePlus and Aeroplan side by side — Seats.aero is a handy free tool for this. Second, credit card point transfers to airline programs can't be undone, so only move points once you've found the seat you want at a price you're happy with.

If you're building a points balance from scratch, Aeroplan's own card offers up to 115,000 bonus points (75,000 after $4,000 spend in three months, plus 40,000 more after $20,000 in a year), while transferable-currency cards like the Chase Sapphire Preferred, Capital One Venture X and Amex Gold all carry strong welcome offers that can be funnelled into Aeroplan later.

Bottom line: Aeroplan isn't automatically cheaper for every United redemption, but for short-haul peak-date economy seats, transatlantic business class, or anyone holding Amex and Capital One points, it's well worth a comparison before you hit book.

Story via The Points Guy.