When, after breast reduction and lift surgery, can I safely raise my arms above my head and travel?

Every surgeon is different when it comes to technique and recommendations. In my practice, you would not lift your arms overhead or lift over 10 lb for 3 weeks. You could travel relatively soon after surgery if and only if you have someone flying with you and that person carries everything. 
With this operation all you see are the cuts on the outside. What you don't see are all of the cuts and tissue movements made on the inside. This is part that is most important and its proper healing is a large part of what determines if you will have a complicated recovery and an attractive outcome. 

I concur with your nurses. 3 weeks is the minimum, with a full month being preferable. Please continue to avoid lifting anything over a few pounds (be sure to get help with your luggage). As always, don’t push yourself even if you’re past the month mark. If something doesn’t feel right or is excessively painful, hold off and try again in a couple of days. 

Every surgeon has his or her own rules on travel.  I recommend an in-office examination as well as a detailed discussion with a surgeon who you are comfortable with.   Finally, make sure your surgeon is a Double-Board Certified Plastic Surgeon certified by the American Board of Plastic Surgery (ABPS), a member of the American Society of Plastic Surgery (ASPS), a member of the American Society of Aesthetic Plastic Surgery (ASAPS), and a fellow of the American College of Surgeons (FACS).Best,Dr. DesaiBeverly Hills Institute for Aesthetic Plastic SurgeryHarvard Educated, Beverly Hills & Miami Beach TrainedDouble Board-Certified Beverly Hills Plastic Surgeon

Dear TexasTeacher,every plastic surgeon has his own postoperative protocol which he recommends to his patients. I would suggest you to discuss this with your plastic surgeon.Daniel Barrett, MD, MHA, MS 
Certified, American Board of Plastic Surgery  
Member, Am. Society of Plastic Surgery

but the implant placement can so if you were over the muscle, ranging of your arms should not be an issue at this point but its best to have the blessings of your surgeon.   Bouncy and strenuous activities are what you must avoid for however long your surgeon decides the restrictions should be in place.  In my practice, the restriction is lifted 3 weeks post-op with patients resuming activities slowly and surely but all surgeons are different.