With the rapid development of aviation communications and the increasing num ber of airborne terminals, it is highly demanded to build up air to air wideband ad hoc networks supporting ultra high speed mobility both in civil and military avia tion systems . Here, the present situation and the developmen t t rend of aviation communication networks are briefly outlined. On the basis of it, the challenging issues of constructing such networks are presented, including the support of ultra high speed mobility, high data transmission rate, long distance single hop links, large scale Ad hoc networking, multiple user ac cess mechanism, as well as their restricted relationship. Finally, physical laye r key technologies and the related research progress for wideband airborne Ad ho c networks are reviewed, including modulation technology, peak to average power ratio suppression in OFDM, frequency offset estimation, channel estimation and c hannel modeling.