In October 2015, I applied for a Recruiting position. Less than a week later, I was emailed to schedule a phone interview. I replied with times and ManTech recruiter never reached out to confirm or discuss another time. I emailed back and and recruiter replied apologizing and agreeing to find another time. I offered another time/day, and again no reply or phone call.
Months later, in January 2017, I applied for an HR position. It was a different person to reach out to me but this time there was no email. I was called out of the blue to discuss position. Person was polite but not engaging and subtly questioning my career choice. I was then invited for an in person interview but recruiter wanted me to come in the next day. That proved difficult but we discussed a possible time for the next day to meet. She stated she was going to call me back later in the day to confirm whether that afternoon time would work. I received no phone call or email.
Unfortunately, my two experiences with ManTech has proved to be unprofessional. However, I'm sure different locations provide different experiences for applicants.