Most Federal agencies require their employees to make reservations for their travel through a travel service which has a contract with the agency. This is the case for me with the U.S. OPM, and as a result, the cost of my travel is significantly higher.
For example, I recently had to travel to Hawaii, and I was required by my agency to purchase an airline ticket using OPM's contract with a travel service. I followed their instructions but also did my own research to compare the cost of roundtrip travel to Hawaii if I purchased the ticket on my own utilizing the internet. I discovered that it cost me $1000 more to use OPM's contracted travel service. I presented this to my agency, but still was not permitted to purchase the airfare on my own and save the government $1000.
The only difference with the ticket purchased through the OPM travel service was that this ticket was a guaranteed one, meaning that this ticket could be cancelled without penalty. To me, this is very expensive "insurance" for an event that rarely occurs. I have flown dozens of times during my 30 plus year career with the Federal government, and have never had to cancel a flight.
Consider this action occuring tens of thousands of times every year, and I can only imagine how much could be saved if Federal employees were given the chance (actually encouraged) to seek out the lowest possible airfare for their travel. All of us do this when we plan our own vacations, don't we? Even if it is necessary to cancel a flight with a non-guaranteed ticket, you usually pay a change fee of $150. This is far cheaper than the cost of a guaranteed ticket.
The cost savings potential for this has to be in the hundreds of millions of dollars. Give Federal employees the permission to exercise good judgement, and feel good about being good stewards with Federal money.
Please note that this affects most Federal Agencies, not just the U.S. OPM.