Delta’s frequent flier program bids farewell to expiring miles

Here’s good news for Delta‘s frequent fliers: Delta SkyMiles no longer expire.

The change came at the first of the year, but so far, no other carrier has followed Delta’s lead.

Here’s a look at activity deadlines set by nine U.S. frequent flier programs, followed by a summary of the perks that elite -- that is, the most frequent -- fliers receive from airlines that track miles rather than points.

Many carriers say miles or points never expire if you have activity in your frequent-flier account at least once in a certain period. Most will restore your miles for a fee, but each program has different rules and fees. Here are the time periods in which you need to have account activity and whether the program tracks points or miles:

--Within 12 months: JetBlue TrueBlue

--Within 18 months American Aadvantage, Continental OnePass, United Mileage Plus, US Airways Dividend Miles and Virgin America Elevate

--Within 24 months Alaska Mileage Plan, Frontier EarlyReturns and Southwest Rapid Rewards.

Shopping with an airline partner or using an airline-branded credit card helps you earn points or miles faster and can help you meet activity requirements between flights.

Loyalty to one carrier improves your odds of achieving basic elite status with airlines that track miles (Alaska, American, Continental, Delta, Frontier and US Airways). Most require flying 25,000 miles (or a certain number of flight segments) a year, except for Alaska, whose MVP tier requires only 20,000 miles. Basic elite status provides:

--Two bags fly free;

--Bonus miles, ranging from 25% to 125%;

--Preferred seating;

--Priority check-in, security screening and boarding;

--Wait list priority;

--Dedicated phone numbers that help if your flight is delayed or canceled.