United is re-thinking its Mileage Plus pricing structure and creating a flexible system that will fluctuate on demand and other factors.

From November 15 the carrier will no longer publish an awards chart. The airline offered this news update on the new mileage reward plans on its website:

"Updates to award travel are on the horizon. For flights on or after November 15, 2019, we’ll no longer publish an award chart listing the set amount of miles needed for each flight."

The details:

• Some award prices will be lower than what’s currently published in our chart. You may have already seen these prices, and you’ll be able to get them immediately.
• Other award prices may be higher than what you see today, especially if you’re traveling at a popular time. These prices will take effect immediately for travel November 15 or after.
• Starting November 15, we’re removing close-in fees, so you won’t be charged the extra fee of up to $75 for booking last-minute award travel.
• A flexible award travel calendar is available on united.com or in our app.

On a FlyerTalk Forum, United noted: “Air awards to US and Canadian destinations that are 10,000 to 12,500 miles today may be available for less moving forward. You might have already noticed these lower award prices, and you'll be able to get them right away. Other air award prices may be higher than what you see today, especially if you're traveling at popular times. This will be effective immediately for travel on or after November 15.”

An update on the carrier's website added: “Increasing award prices for the most in-demand flights allows us to offer lower prices on other flights. If your award travel is flexible, these updates will help you make the most of your miles.”

In an unexpected and generous move, the carrier also announced the removal of “close-in fees” from November 15, so members will no longer be charged up to $75 for booking last-minute award travel. However, United will not be refunding fees paid prior to November 15, even if travel occurs on or after November 15.

However, passengers will be unable to monitor and predict their mileage moves as the number of miles needed to book any given flight will be presented only at the time of making a booking. Today’s fixed rates will apply to travel through November 14.

With no published award charts, mileage costs will be able change at any time and without notice. Thus rewards passengers will have to continuously check with the airline, or else take a chance and lock-in any upcoming travel plans to avoid the cost of those journeys going up unexpectedly.

Dynamic pricing is already in effect on some routes, such as between Los Angeles and San Francisco. Business Traveller Australia notes that a published award chart sets a fixed rate of 25,000 miles for a one-way ‘first class’ (business class) flight, or 10,000 miles in economy for the short California flight. However, for travel beyond November 15, departure dates searched by the publication revealed the same one-way economy hop priced at either 6,500 miles, 7,000 miles, 12,500 miles, 15,000 miles, 18,000 miles or 20,000 miles, depending on the day and the departure time of the flight.

In most cases, all flights departing on the same day showed the same reward cost, although on some days -- say the during Christmas holidays -- choosing one flight over another could require almost three times as many miles.