Das uses smaller version of Kirpan on air.In UK, India,Russia and UAE,it is fine.
Das has worked with the securty agency.As per law in India,we can have Kirpan on all domestic flights but shoulkd be less then 6' and blade not more the 2.5'.And some time this law could be suspended after 9/11 and in past Pro Khalistan guys did highjacked Indian plane with Kirpans.
But at present planes are such that,that they can be highjacked but soon,we will have a sort of plane taking half hour from London to newYork and to open the cockpit,it may take 45 mintutes.Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=14188
Only way that could be left would be crash the plane due to de comprression as that plane will be not in air but more in 'space' or outer ost fringe of atomsphere.
So we can have knife proof windows in which first iron grill needs to be broken before glass can be broken.Or in emergeny an iron grill can cover glaass.
We some time have to think like a terrorist before we actuly make way to conter them.
So some one can take our guise and can highjack if large Kirpan is there.
But if we have locks of speacial types provided by air authorities,then can surrong our Kirpan during flights and can be opened after flight is over.Therre could be some practialce problems in that but we can over come that.Sky Marshalls can be trained to over come knife attacks also.Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=14188
Lastly,it is fact that to be Singh,we have to get baptised.And after that we have to have Kirpan or Kirpa Pan or Hand of mercy by Akal.
But as we are told to use Kirpan to protect and not to kill,but someone not among us but posing like us can create problems.But this situation will change one day.
Even after wearing small Kirpan during air trevel,das use to go to Gurudwara,to seek pardoning for adjusting to present circumstances,not our fult nor the fault of authorities but due to evil Jehadis.