Last month, I traveled to London with my 6-month old baby... solo! My husband was already in Paris for business and we were to meet up in London. At 6 months old, my baby was already sitting up, although still a bit wobbly. I had to really plan ahead how I was going to get through security, etc. with him... by myself.
For sure I was taking his stroller on this trip. And just like the last couple of trips, I shared a big suitcase with him. That allowed me to push his stroller with one hand while pulling the suitcase with the other. The key is to limit the amount of stuff you have to handle, the less the better. In addition to the suitcase, I had two bags that I carried with me to the plane - the baby's travel diaper backpack and my camera bag. Both bags fit under or hang over the stroller perfectly.
I gate checked the stroller, but that meant I had to fold it to get it through security. In order to do that while still holding on to the baby, I had him in a baby carrier. The security in Houston allowed me to go through the metal detectors while my baby was still in baby carrier. They just tested my hands for residues after I went through.
After I went through security, I put my baby back in his stroller until we boarded the plane. During boarding, once again he was in the baby carrier while I folded the stroller to put it in it's gate check bag.
During the flight, the baby carrier came in handy when I needed to use the toilet and when he was fussing and wanted me to walk around.
Once we landed and we got his stroller, I put him back in it. After being in my arms for 9+ hours, he was very happy to be in his stroller. It also made it easier to go through immigration and pick up our suitcase.
How do you manage on your own?