Dell Mini 9 battery not recognized

This might help:
https://help.ubuntu.com/11.04/ubuntu-help/net-wireless-airplane.html

Or, there may be a setting explicitly for Airplane Mode in System Settings > Network. (I don't have an Ubuntu 11.04 system on hand right now to check.)

This is not the same as the airplane mode with 8.04. It only seems to affect ten wireless card, and not the battery. Is 8.04 available for download somewhere online still?

You can download DVD images for Ubuntu 8.04 LTS at http://cdimage.ubuntu.com/releases/8.04.4/release/. However, please note that, except for nongraphical servers utilizing only a subset of available functionality, Ubuntu 8.04 LTS is no longer supported, which means, among other things, that (1) you won't be likely to get very good help with it here, and (2) you won't receive security updates for newly discovered vulnerabilities. Because of that, I recommend against using Ubuntu 8.04 LTS.

Hopefully someone knows a way to achieve the same effect as enabling airplane mode, on Ubuntu 11.04, and will post here about it. Alternatively, you might try Ubuntu 10.04 LTS, which is still supported.

Flight mode on my phone disables all wireless connection. On my computer I click on the little wireless symbol on the bar in the top right and uncheck "enable wireless".
You said though that your battery wasn't being recognised. I had a problem where my wireless could not connect unless my battery was fully charged and the computer plugged in. If this is what you mean then I to have been waiting for a year to solve this one. Yesterday I finally found a solution. It seems somebody decided to put a script in that fiddles with the wireless when I'm on battery for some reason. This file is /user/lib/pm-utils/power.d . near the top of the file are the following lines:

get_wireless_params() {
    # $1 = interface
    # $2 = on or off
    unset iwpriv iwconfig iwlevel
    # added the following line.. take it out if it doesn't work
    # Don't do anything if we cannot find a driver for this iface.
    [ -L "/sys/class/net/$1/device/driver" ] || return 1
    # Skip if not a wireless card.
    [ -d "/sys/class/net/$1/wireless" ] || return 1

I added one line (the one in the middle) with sudo gedit :

get_wireless_params() {
    # $1 = interface
    # $2 = on or off
    unset iwpriv iwconfig iwlevel
    # added the following line.. take it out if it doesn't work
    return 1
    # Don't do anything if we cannot find a driver for this iface.
    [ -L "/sys/class/net/$1/device/driver" ] || return 1
    # Skip if not a wireless card.
    [ -d "/sys/class/net/$1/wireless" ] || return 1

Now I can connect even when I am unplugged no matter how much charge is left on my computer.

As a side note, I have an acer timeline x 1830T-68U118 and in order to get it to run in the first place I have to execute the line.

sudo modprobe -r acer-wmi

It would be nice if the next version of Ubuntu would recognise my computer and do these things for me.