I can "concur" that being an external consultant, often with support of C level, helps.
Though I was once an employee, I can justify anything.
It doesn't take much justification to not want to fly United, American or Delta sometimes. I need to get to Milan from New York, and I want a full day in the office. Leaving at 6pm ( United) does not allow for that. Leaving at 10pm does. Thats it, EK JFK-MXP, end of story.
That flight leaves at 10pm
US Flag carriers, which I personally hate to fly, going to Europe, all have departure banks that leave early in the evening, 6pm-9pm. Foreign flag carriers, often have multiple departures of the day, and often tend to leave later. All the US carriers leave Europe between 8am and 12 max, European time, except London. going to US. I like to leave London as late as possible and only BA has the latest flight of the day.
This is easily justified, since I am sure the clients want to avail to the maximum work day, especially since they are paying for it. I'm just maximizing my work day.
Most travel management programs has a human travel agent backdoor that can easily book directly to a GDS. I sometimes use that also.
As long as the expense does not go over budget, and is not glaringly out of wack, i.e Booking EK F JFK-MXP at a significant expense, when only J is allowed, i have never gotten into trouble for booking what I want. The key is to have enough funds in the travel budget line, and i have control of that also.