Yes, a Gillette Mach 3 and other similar cartridge razors (like Venus or Harry's) are perfectly allowed in both carry-on and checked luggage in 2026. These are classified as "disposable" or "cartridge" razors where the blade is permanently embedded in a plastic housing, making it impossible to use as a weapon. This is the same rule that applies to standard disposable plastic razors. However, it is important to distinguish these from Safety Razors (the metal ones where you can unscrew the head and remove a sharp, loose blade) and Straight Razors (the "cut-throat" style used in barber shops). For those types of razors, the handle is allowed in a carry-on, but the blades themselves are strictly prohibited and must be packed in checked luggage. Since the Mach 3 blades are safe and encased, you can bring your razor and spare cartridges through the security checkpoint without any issues, provided your shaving cream or gel is in a container of 3.4 oz (100ml) or less.