I know some people may think that vacation time should not be relevant in choosing a major, but my favorite thing to do is travel so it is important to me. Obviously the more PTO the better, but having a job that would allow me to do things like take unpaid time off, work on holidays to save PTO, or leave early on certain days would be beneficial. Even working from home sometimes would be helpful, as I don’t mind doing a little work while I am travelling; I just like experiencing different places. Without factoring these things in, my preferred major is Civil Engineering, so are there any such jobs under that major? Thanks for your time.
Good question, I would also like to know.
Software development contractor.
Keep in mind that Engineers are paid well, because they are viewed as important or critical to the operations. That doesn’t usually equal lots of flex time.
If you’re looking at flexibility, look at the type of work being done. If it’s the day to day operations of a plant, warehouse, transportation/logistics, etc…, then you likely have more flexibility (and your work can be covered by your peers). If it’s a “project” specific role, then deadlines have to be met, and you’ll need to schedule PTO (more than a few days) in-between projects.
In general, it’s the type of job/field you choose that impacts how flexible is the work environment, more than simply your major.
A personal anecdote that gives you an example of what is possible -
For many years I was part of a field service organization supporting large power plants. The reality of power demand is that the utilities performed repairs/maintenance in the spring/fall during the change of seasons. This also meant I worked in the office and on the road 12-13 hour days, 7 days a week for 4-5 months a year. As a salaried employee, the company did not owe me any overtime, but they at least recognized our customers had been billed for a ton of hours. So we were given a choice - overtime at 0.5x rate or time off at a 1x rate. Having all that time off was great, but I will admit the long spring and fall work hours got old and I moved on.
The real challenge for you is how to find an employer with such a policy without making them think all you want is time off. In my case, the job is what I wanted, but the time off was a nice benefit.
Civil. This is because civil engineers are far more likely than other engineers to work for government agencies (public works, highway depts, water agencies, building depts, environmental agencies, etc). As a gross generalization, public sector engineers have lower salaries but better benefits than private sector engineers, including better vacation policies and retirement plans.
Of course, many civil engineers also work in the private sector, and in that case I don’t think they have any particular advantages in terms of vacation.
Or you can (eventually) become a consultant and work for yourself. 
That’s what my husband and I did - we are structural engineers. The downside is we work a lot of nights and weekends, but DH did that working for another firm, anyway! And we schedule vacations when we want. We built an addition with an office onto our house, so we have no daily commute to endure, either. It’s not for everyone, but it’s been 18 years for us and we like it a lot.
The company may make more of a difference than the field. Example link…
https://www.glassdoor.com/blog/25-highest-rated-companies-for-vacation-paid-time-off/
To me it seems that more starting engineers get three weeks of vacation than when I started in 1984 (2 weeks for the first 5 years. But with quick google search, I was not able to prove it true or untrue.
I know the state and federal engineering has a decent amount of flexibility that varies… In federal I have classmates that get to attend day classes because they can telecommute and have flexible work hours… In my CA state department, a lot of people take off time every week because you get 11hrs / mo start to 18 hrs / mo after 20 years of service. +3 personal holidays and 2 weeks incentive bonus time a year. Lol, they let you take time off for a lot of things but they’ll frown on you when you want to use it for grad school.
I would say it’s a disadvantage rather than just not an advantage. Civil engineers are often project-based and need to work to meet the deadlines of the construction. I work for a construction manager and have called civil engineers on Saturday from time to time to get questions answers, things redesigned, etc for urgent items that come up all of a sudden and can’t wait until Monday.