Depending on the capabilities of the APs, the following flags can be included in the output:
E - Extended Service Set (ESS). Indicates that the station is part of an infrastructure network (in contrast to an IBSS/ad-hoc network).
I - IBSS/ad-hoc network. Indicates that the station is part of an ad-hoc network (in contrast to an ESS network).
P - Privacy. Data confidentiality is required for all data frames exchanged within the BSS. This means that this BSS requires the station to use cryptographic means such as WEP, TKIP or AES-CCMP to encrypt/decrypt data frames being exchanged with others.
S - Short Preamble. Indicates that the network is using short preambles (defined in 802.11b High Rate/DSSS PHY, short pre- amble utilizes a 56 bit sync field in contrast to a 128 bit field used in long preamble mode).
s - Short slot time. Indicates that the network is using a short slot time.
Please add this to FAQ and WIKI