LOR for 153A?

Complete the SIFT and the flight physical as the CW3 will want to see you’re qualified. Bring the rest of your packet, sample at http://www.gowarrantnow.com. Then go to the local CAB and ask for the CCWO he will assist. Do not be scared they do this all the time, they will ask questions. Just think if you want this and get it they are simply just further along and you will one day be the LOR writer!

1SG
Warrant officer recruiting company

It's a tricky requirement, isn't it? A letter of Recommendation from someone you never worked with, from a field you never worked in.
Print your ERB and DA 705, go to an aviation unit and ask if you can make an appointment with any CW3 pilot to talk about an LOR. If you are working directly with a recruiter on this, ask if he/she can set up that appointment with a CW3 at an aviation unit.
Be ready to answer questions about why you joined the Army, what you have done so far, and why you want to be a pilot, and what your career goals are.

I believe the requirement is for the LOR to be from a senior Army aviator. Any aviator regardless of rank could be your man. Make sure they are a senior or master aviator. If they are wearing their aviator badge, a star or a star and a wreath will let you know if they are senior or master. I was a W2 with a senior badge and I've seen CW5s with the basic "slick wing" badge. Good luck.