Flight/Substitution

I have used the substitution in the past, but this time I will be flying across the country for a third round interview in which I just may get tested. Since this interview will be with a medical-based company, I wouldn't doubt a drug test prior to employment although they have not mentioned anything of the matter yet.

The first question I have is if anyone has had a drug test on their third round interview, or x'th round, with any company during the interview process or is it more expected to be tested upon being offered the job?

Second question, regardless of the first, is if anyone has taken someone elses urine on a flight across the country?

I would assume its safe to use a shampoo bottle(any other suggestions welcomed) in your luggage that goes underneath the plane, however I would never take it with carry-on due to the fact that I could be searched prior to boarding the flight.

I am not even sure if the urine would stay cool enough for 6 hours worth of flight but if I remember correctly, my luggage has been cold when getting it back in the past. This is another concern. I could try to wrap it in some kind of insulation or freeze it but I would not want it to look sketchy if they were to x-ray the baggage or hand search it. My friends have told me they have gotten luggage back where it was obvious it was searched (everything stuffed back in).

Don't worry, I am not a doctor so I wouldn't be directly involved in any medical process ;) but I appreciate any responses or opinions relating to the matter. Its funny how I searched the forums and found nothing related. Just for extra info, I stopped smoking days ago, but the interview is less than 2 weeks away and I am aware it may just take a bit longer to get clean since I have smoked basically everyday.

Thanks!