Despite a better economy and more travelers wanting to take domestic flights, average U.S. roundtrip airfare prices have risen by about $14 during the first six months of the year compared to that same period last year.

The average roundtrip price for a flight within the U.S. during the first six months of 2014 was $509.15. Domestic airfare is outpacing inflation as well, rising 2.7 percent compared to the 2.1 percent in the Consumer Price Index (CPI).

In the last five years, airfare has gone up 10.7 percent -- after adjusting for inflation -- according to an Associated Press analysis of data from the Airlines Reporting Corp. The company analyzes data from ticket transactions from over 9,400 travel agencies and discount airfare websites like Expedia and Priceline.

Although demand is going up for airfare as the economy recovers, prices are still going up.

"Airlines have reduced the number of seats while more people want to fly because of the economic recovery. All this leads to higher airfares," said Chuck Thackston, managing director of data and analytics at Airlines Reporting Corp. "This trend in airfares is likely to continue for the near future, as the economy continues to grow." 

The majority of travelers fly for business. With the improved economy, more businesses are sending their employees on trips that include domestic airfare. With data released last week from the government showing economic growth after a long and cold winter, businesses are also doing more hiring and consumers are spending more.

The rise of airfare doesn't include the fees that have continued to increase and be added to customers' trips. These extra fees started with baggage fees in 2008. The baggage fees were designed to offset rising jet fuel prices.

Now, besides baggage fees becoming a standard for almost all carriers, domestic airlines have added fees for extra legroom, early boarding of the plane and even carry on baggage. That's despite jet fuel being 7.2 percent lower this year than last year when purchased by airliners ($2.96 per gallon). 

Airliners aren't passing on their savings on jet fuel to their customers. A good reason for that is fewer choices, thanks to fewer carriers.

With mergers and combined airlines, there is much less competition and therefore less price compeition between airliners. The big four carriers of American Airlines, Delta, Southwest and United control more than 80 percent of the domestic air-travel market. Discount airlines like Spirit and Allegiant have tried to lure passengers in with their no-frills cheap airfare but haven't been able to compete with the Big Four.

Airlines for America, the industry's U.S. trade and lobbying group, said passengers shouldn't blame airliners but the government instead. With a new $5.60 flat fee (each way) installed by the Transportation Security Administration, airliners felt that they had to raise prices.

Fees and taxes on airline tickets are just a small portion of the ticket, however. On a $500 roundtrip flight between New York and Seattle, only 12 percent goes to taxes and fees, and the rest goes to the base ticket price.