Yes, you can check a 28-inch suitcase as long as it does not exceed the weight limit set by the airline. In order to be accepted as standard checked luggage the weight should be within the limit of up to 50 or 70 lbs. That being said, some airlines will accept oversized bags up to 126 linear inches (320 cm).
On domestic flights within the United States, a carry-on bag that's smaller than 22 x 14 x 9 inches (45 linear inches), including handles and wheels will meet the size restrictions of all major airlines, such as United Airlines and Alaska Airlines.
Measuring the size of your luggage isn't tricky. Most airlines require that your bag be 62 linear inches or less. Therefore, your bag's length, width and height cannot exceed 62 inches. This measurement includes the wheels and the handle of your luggage.
For example, the Samsonite Winfield 2 28-inch checked suitcase has the total overall dimensions of 31 (height) x 20 (width) x 12.75 (depth) inches. To get linear inches, we need to add up 31 + 20 + 12.75, which equals 63.75 linear inches.
Because softshell luggage has more give, a hard shell suitcase can be better at protecting fragile contents, assuming you cushion it well inside. On the other hand, that rigid exterior makes hardshell bags unable to be compressed to squeeze into tight spaces like softsided bags are more apt to allow.
You should check with your airline first, but most domestic airlines permit a carry-on piece of luggage that is 45 linear (total) inches. A common sized bag for carry-on luggage is 22x 14x 9. Most airlines have a carry-on weight limit of 40 pounds.
If your carry-on is oversized (and doesn't physically fit inside the overhead compartments) or you encounter a strict airline employee, they will ask you to check it in at the gate.
30-inch luggage is one of the largest options, so it's going to weigh more than a 26-inch one or your carry-on. Most airlines have a maximum weight limit of 50 pounds per checked bag. This limit does not take into account size, so 30-inch luggage needs to meet the same requirements as 26-inch luggage.
Checked LuggageThe most common maximum size bag allowed is 62 linear (total) inches. A common size bag for checking through is: 27 x 21 x 14. Airline carriers will allow overweight, oversize or additional baggage for additional fees.