For business flyers like Adam Kubryk, who is on the road about 200 days a year, one of the perks of flying often and using the same airline regularly is getting upgraded from coach to business class when a seat is available.

But now when he flies on Delta Air Lines on some of his more frequent work-related routes, he has lost that key perk and it is making him mad enough to ditch the airline and take his frequent flyer miles elsewhere.

The issue: in March, the airline stopped offering upgrades for flights between New York and Los Angeles, San Francisco or Seattle.

Delta had previously offered upgrades on these cross-country routes to high-level frequent flyers when the seats were not sold. Now frequent flyers say they are seeing empty business-class seats while being told that they are no longer available to passengers who do not specifically pay for those higher-priced seats.

“It blows my mind that they’d rather keep those seats empty than keep my loyalty,” says Kubryk, 31, a New York-based hotel furniture salesman.

Undoing upgrades on those routes comes amid a swirl of other changes for frequent flyers, but particularly those who fly Delta. The biggest change, calculating points earned based on money spent rather than miles flown, favors business travelers who are the most likely to pay top-dollar prices for last-minute bookings.

The change in how miles will be calculated is scheduled to start at the beginning of 2015. The airline also revised its frequent-flyer award levels for next year.

Delta spokesman Paul Skrbec notes that the company’s change to its upgrade policy comes as the airline is making major investments to upgrade amenities on those routes. That includes seats that turn into beds, improved entertainment choices and “premium dining.”

He also points out that at the same time the airline was taking away upgrades on the routes to and from New York, it was adding upgrades on flights between Hawaii and Los Angeles, Salt Lake City, San Francisco and Seattle.

On Delta’s improved Boeing 757s used on transcontinental flights, the coach section will get a makeover, with 44 “Economy Comfort” seats with more legroom and greater seat recline being added (plus 108 regular seats).

All economy seats will have a USB port and an outlet, plus a nine-inch video monitor. You get a 16-inch monitor in Delta’s BusinessElite cabin.

Your Choices

For those who want to remain loyal to Delta and want to fly business class, your primary option is to pay for it. A “Global Upgrade”—a bump-up available for any route—could be used, but frequent flyers say those tend to be used on more costly and longer international flights.

That fancy business class seat will not come cheap. A sampling of non-stop New York to Los Angeles roundtrip flights on Delta, using a five-day stay available with one-week’s notice had a range of $962 to $1,205 for economy and $4,578 to $5,216 for business class.

Flyers who switch over to another airline may have more luck getting upgrades. Other airlines have similar or even better amenities than what Delta is adding, says frequent flyer expert, Brian Kelly, who runs ThePointsGuy.com.

Besides similar amenities on United Airlines and American, JetBlue is launching a first-class service in June called “Mint” on flights between New York and Los Angeles or San Francisco.

But other airlines still allow their high-level frequent flyers to upgrade.

American allows its elite-status passengers to get upgrades 72 hours in advance, and United allows its top passengers to cash in miles or reward certificates to bump up their seating.

While airlines routinely tweak their mileage programs, Kelly says Delta’s policy change is particularly harsh because it gambles that enough people will want to pay for the seats at the expense of loyalty customers.

“It’s the straw that’s going to break a lot of elites’ backs,” he says.

That includes Jason Schlossberg, 40, who regularly flies from New York to San Francisco on Delta. The president of New York-based public relations firm kwittken + company says he was routinely upgraded until a flight late last month, which is when he realized the policy change had taken effect.

After that surprise, he says: “I’m going to be looking into this issue much more closely than I have been, after experiencing this first-hand.”

Play The Game

Another alternative that gets a lot of attention among serious frequent flyers is playing the airlines off each other.

Delta frequent flyer Richard Laermer, 52, says he is not happy with Delta, so he is planning on checking what is available for him if he changes camps through a process known as “status match.” That allows elite flyers to trade on their status with one airline and get elite perks with another.

To get a status match, travelers must contact another carrier’s frequent flyer program and make the request. The standards vary by airline—not every airline will go after every other airline’s customers—and typically the airline you are switching to will require a certain amount of new travel to qualify.

There are even promotions to draw in rival airlines’ top passengers.

United, for instance, is offering platinum-level flyers from Delta and US Airways platinum level status on United for 90 days through the end of May. That can be retained if they fly at least 18,000 miles or 22 flight segments during that period.

But rather than bringing most of their business to a single airline—Kubryk says his company spent $42,000 for his Delta flights last year – business travelers could perhaps just do what most consumers do: shop for the best flights each time they fly.

(Editing by Beth Pinsker and G Crosse)