Great question. The answer is yes but I wouldn’t call it “at risk” because that’s not always a bad thing. This actually a fairly complicated subject but I’ll try and break it down (somewhat generically) and hopefully it’ll make some sense (clarity isn’t always my strength).
Ok as a pilot you will either have be a “lineholder” (aka hold a line, bid-line, bid,etc) or be on reserve. All pilots will also have a minimum guarantee (typically around 75hrs). Now if you have a line that line will be a minimum of 75 hrs (to cover the guarantee) to a maximum just under 100hrs (the FAA legal limit). Now most pilots bid a line as soon as they can hold one seniority wise because they want to know where, when and with whom they’re flying. Reserve you may fly, you may not, you’ll go wherever is needed, with whoever whenever. Typically that will mean less desirable trips (redeyes, low “credit”, lousy overnights) with less desirable pilots hence the attraction to getting a line. This is worse if you commute because you need to be close to the airport and if you don’t fly you’ll need a place to stay (aka crashpad) which is an additional expense while you’re struggling as a new guy. This all sounds pretty bleak BUT there are exceptions depending on your personal sitch making reserve actually desirable.
Take me for example. I don’t commute, I live on Oahu, my company has a 3 hr callout for reserves (meaning I have 3 hrs to get to the airport) and there’s literally nowhere I can go on this rock that’s more than 3 hrs from HNL. So commuting not an issue (was the same when I was EWR based and lived in NY 30 min away). Now on the Airbus we go JFK, West Coast, Australia, Asia and the South Pacific. Now let’s talk lines again. As I said lines will vary from 75-100hrs (min being the 75) and there are any number of ways to get to those numbers. All trips have a “credit” value based on the projected flight time of the trip. On the Airbus they range from 12hrs for a West Coast trip (say HNL-LAX-HNL) to 22 hrs for a Beijing and back. Either way your gone 2-3 days but you can 4 PEKs, earn 88hrs of pay, work only 12 days and have 18/19 off OR you can do 7 LAXs, earn 88hrs, work 18 days and only have 12 off. Obviously the better lines have better value trips so your work less and get paid more. Now at my relatively low seniority I’d be doing the 7 LAXs, probably redeyes with min days off. I therefore bid for a Reserve line. Why? Well we’re properly staffed (meaning most trips are covered unless someone’s sick or something breaks), I’m guaranteed 75hrs of pay but typically only fly 40-50hrs. While I’m only guaranteed 12 days off I typically end up with 18-20. The icing on the cake is the will often call me for a trip on a guaranteed day off in which case I get paid for that ABOVE the 75hrs which usually brings me up to the 87-95hr mark in pay (again while only actually flying 50-60hrs). I’m pretty easy going so I don’t worry too much about who I’m flying with and most of our overnights are pretty good. In short Reserve is actually a really good deal for me.
I hope that makes sense?