DON'T PUT ON A REC LETTER UNLESS IT WILL DEFINITELY BE SENT!!!
Here is a note from my pre-med advisor:
"Note of caution on outside letters. AMCAS will process and send out your application whether or not the committee letter and other recommendations have been received. Yet, when you list their names on AMCAS, medical schools will be waiting for their letters before they review your file. Be sure that the recommender will be able to get the letter in this summer. Many medical schools start reviewing files at the beginning of August (some even in mid-late July).
I had a situation a few years ago where an alumna started working for a prominent scientist in June following graduation, and the PI was going to send in a letter at the end of the summer. The PI never got to it, and into late October the alumna had no interview offers. In order to get schools to start reviewing her file she had to tell AMCAS that the letter would no longer be sent. Once you submit AMCAS with recommenders listed on the application, you can not delete the names. For that alumna, AMCAS then lists "letter no longer being sent." Soon after the interview invitations started in, but a lot of the fall dates were filled by then so she was interviewing into January. At schools that interview the entire pool first (Penn, Harvard, etc,) that is not a problem but for rolling admission places it can be. In addition she had to explain in some interview that she was still working in the same research group but that the PI was so busy that he never got to it. Recognizing the name the interviewers understood but in a few situations responding to the question was a bit awkward."
Best,
C
