I hear what you are saying. But, for this f/a's medical condition it does state under the ADA: Once the employer is notified of (I wont say what this f/a has) the company must accommodate the employee as long as it doesn't cause undue financial hardship to help reduce the employees absenteeism. AA has known about this for over 1 year and have not done a thing to accommodate this f/a to reduce absenteeism.
We (and that may include you) do not know the entire story. Large corporations (and that includes AMR) do not go out of their way to violate the major work-related legislation. There is just too much bad press associated with such actions. (Now, if they could do it without the public finding out, well, game on.

)
One would need to know this f/a's attendance behavior prior to the current health condition. I'm not saying she did, but did she call in sick frequently to get out of trips she didn't want to work? Was she one of the accrue-a-day-take-a-day girls. I know f/as who view sick leave as supplemental vacation. I heard one f/a say, "I earned that sick leave. It is my right to use it any way I want." She found out otherwise. She is no longer with us. She was terminated for failing to come to work on a regular basis. Sick leave is not a right, it is a company benefit. Taking sick leave for any reason other than being sick is a termination offense. A lot of us don't realize that a great number of American workers today do not have paid sick leave. There is no Federal law (and never has been) that requires company's to provide paid sick leave. It was started as a company benefit to attract workers to companies. (Actually, if I remember correctly, it was unionized workers who first had paid sick leave. What a surprise!)
If a f/a accrued 400-500 hours of sick leave without taking much (or any) time off, then became seriously ill, I imagine the company might be more lenient that if a person developed a serious illness after a number of years with the company, and it turned out they went into the illness with 50 or so hours of available sick leave. Companies also look at what are referred to as "patterns of behavior."
If you have been sick every Thanksgiving and Christmas for several years because you don't have the seniority to hold off those holidays, your case is weakened when you ask for leniency. I use to have to deal with this stuff all the time when I was in the oil business. People couldn't believe that we were not granting them additional time off when they had never managed to accumulate even a whole week of sick leave. And, at the oil company I worked for, you accrued a whole day of leave for each month on the payroll, and as soon as you finished your 6-months of probation (no paid sick leave during), you were given a whole years' worth of leave (12 days) to give you a cushion; so, by the end of your first year, if you didn't call in sick, you had 18 days of leave accrued.
I noticed a couple of comments that the "arbitrators tend to side with the company." It's not so much that, it's just applying the law. I mean can you imagine an arbitrator asking a f/a, "did you understand that sick leave is to be used only for times you are sick?" And, the f/a replying, "I earned that leave. I can use it for anything I want." Or, "I don't like working weekends; so, I called in sick."