Boeing 'tried' in the sense that they said "We will try if the government pays for it". And also by 'tried' it means 'we propose an absolutely outrages design, to make sure it appeals to politicians and we can get money for it for the next 15 years.'.

As soon as the government money was gone, Boeing threw the plans in the trash. Everybody else who was competing for government money instantly threw their plans in the trash as soon it was clear no government money was coming.