OK so here is what I learned about the "close the lid" style bassinet --

We contacted UA in advance to register the fact that we had a lap infant and request a bassinet when flying in J on a BOS-SFO flight operated by a 28J 757-200 (one of the converted UA p.s. planes of the former three cabin era).

United's online description of this equipment doesn't say there is *any* fixed bassinet (they list this as version 2, 28/114, https://www.united.com/web/en-US/con...0/default.aspx , and list "-" under fixed bassinets section for the Business cabin).

We assigned ourselves seats 5EF which, based on photos of the cabin, seemed like it might have a bassinet. We weren't sure, thought we would experiment.

At the gate, a few minutes after we requested gate tags for our stroller/car seat, a gate agent paged us. They said they noticed that our PNR included a request for a bassinet and told us that according to the FAs, this equipment *only* has bassinets in J at 5AB. 5A was empty, and they were kind enough to page pax in 5B and ask her to trade for 5E, which she was happy to do. So we ended up with seats that putatively have bassinets.

We boarded early and inspection revealed that there were fixed in-bulkhead bassinets available at both 1AB and 5AB. (There are also compartments in the other bulkhead seats, but whatever is in 1EF and 5EF seems to be equipment or storage; 5EF looks like it's labeled as medical oxygen.)

So here is the deal with the 5AB bassinet:

Yeah, it's like a baby bucket that you can put the baby in, and if they cry you can close the lid

But really, it's like a little recessed storage compartment -- maybe 12 inches deep and kind of oblong in shape -- which you can put a baby into. It's a hard surface. It's not huge -- a little less than a meter across, and at its widest point maybe 18 inches long, tapering to a smaller size on one side. Our baby does fit inside but he fills maybe 75-80% of the available space (he's 3 months old and is at about the 10th percentile for weight and 80th percentile for length among babies of his age and gender).

The FA offered some blankets (both the J blanket and some Y blankets); I ended up trying out a single Y blanket folded over itself and covered with our on-the-go changing pad, which seemed to make a nice, soft, low-suffocation-risk "bed" in the hole. There's a little mesh cover which I at first thought was some kind of baby hammock but it's actually meant to snap in place on top of the baby, kind of like a seat belt. Possible that a sleeping baby in the bassinet with the cover installed is safer for turbulence than a sleeping infant in arms with a parent wearing a seatbelt.

You're meant to keep the cover open while it's in use as a bassinet. The lid stays upright in this position. There's a little mirror on the inside of the lid which you can use to watch the baby; this is good because, sitting down in the J seat, you cannot see into the compartment at all (baby is sort of at the same eye level as the center of the personal IFE screen). Seems secure and basically safe (modulo concerns about suffocation risk with any padding). Logistically, really interesting.

Baby hated it tho.