1.  up in the air(s = adj.all) - very uncertain; "left everything up in the air"

2.  up in the air(s = adj.all) - not yet determined; "plans are still up in the air"

act up, active air defense, add up, air, air alert, air attache, air attack, air bag, air base, air bed, air bladder, air brake, air brush, air bubble, air built, air castle, air cell, air chamber, air cleaner, air cock, air combat command, air compressor, air condition, air conditioner, air conditioning, air cooling, air corps, air cover, air crew, air current, air cushion, air defense, air division, air drill, air duct, air embolism, air engine, air express, air filter, air flow, air force, air force academy, air force intelligence surveillance and reconnaiss, air force isr, air force officer, air force research laboratory, air force space command, air gap, air gas, air group, air gun, air hammer, air hole, air horn, air hose, air hostess, air jacket, air lane, air letter, air level, air line, air lock, air mail, air marshal, air mass, air mattress, air medal, air mile, air national guard, air out, air passage, air pipe, air plant, air pocket, air poise, air pollution, air potato, air power, air pressure, air pump, air raid, air reconnaissance, air rifle, air sac, air search radar, air shaft, air sick, air sickness, air sock, air space, air speed, air spring, air station, air stove, air terminal, air thermometer, air traffic, air transport, air transportation, air transportation system, air travel, air traveler, air traveller, air unit, air vessel, air wave, air well, ante up, back up, backed up, ball up, balled up, bang up, bear up, beat up, beef up, beefed up, belly up, belt up, bind up, blaze up, block up, blow up, blowing up, blown up, blue air, board up, bob up, bollix up, bollixed up, bollocks up, bolster up, bomb up, bone up, book up, boost up, botch up, bottle up, bound up, box up, brace up, break up, breath of fresh air, brick up, bridle up, bring up, bringing up, brisk up, bristle up, brush up, bubble up, buck up, bucked up, build up, bump up, bunch up, bundle up, buoy up, burn up, bust up, butter up, button up, buy up, call up, calm air, carve up, cast up, castle in the air, catch up, catch up with, caught up, caught up in, chain up, chalk up, charge up, chat up, check up on, cheer up, chew up, chin up, chirk up, chock up, choke up, choose up, chop up, chuck up the sponge, chum up, churn up, clam up, clap up, clean up, clear the air, clear up, climb up, clock up, clog up, close up, cloud up, clouding up, clutter up, cobble up, cock up, come up, come up against, come up to, compressed air, conjure up, cook up, coop up, cork up, cotton up, cough up, coughing up, couple up, cover up, cozy up, crack up, crank up, crap up, creep up, crock up, crop up, curl up, curled up, current of air, cut up, dam up, dead air, deck up, dig up, digging up, dish up, divided up, divvy up, do up, doctor up, doll up, dolled up, done up, dope up, double up, drag up, draw up, dream up, dredge up, dress up, dried up, drink up, drive up, drive up the wall, drum up, dry up, drying up, dummy up, earth up, ease up, eat up, edge up, end up, even up, face up, face up to, faggot up, fake up, fancied up, fancy up, fatten up, fed up, felt up, fess up, fetch up, fig up, fill up, finish up, fire up, firm up, fix up, flame up, flare up, flow of air, fluff up, fog up, fold up, follow up, follow up on, foot up, fork up, fort up, foul up, frame up, freshen up, fuck up, furbish up, gang up, gang up on, gas up, gather up, gear up, get up, ginger up, give up, giving up, glam up, go up, go up in smoke, gobble up, grow up, grown up, grub up, gum up, gummed up, gussied up, gussy up, ham it up, hang up, hard up, hash up, haul up, head up, heap up, heat up, heated up, heave up, heft up, held up, het up, high up, higher up, hike up, hit it up, hit up, hitch up, hive up, hoke up, hold up, hole in the air, hole up, hook up, hook up with, hop up, hopped up, hot air, hot up, hung up, hurry up, hush up, hype up, ice up, in the air, industrial air pollution, jack up, jazz up, jolly up, juice up, jump up, jumping up and down, keep up, kept up, key up, keyed up, kick up, kink up, kit up, knock up, lace up, laid up, land up, lap up, laugh it up, lay up, lead up, let up, lift up, light air, light up, lighten up, limber up, line up, lined up, link up, liquid air, live it up, live up to, liven up, load up, lock up, log up, look up, look up to, looking up, loosen up, louse up, made up, make up, make up one's mind, make up to, mark up, mat up, matte up, measure up, measure up to, meet up with, mess up, messed up, mix up, mixed up, mock up, mop up, mount up, mount up to, move up, muck up, mucked up, muddy up, muffle up, mug up, muster up, naval air warfare center weapons division, offer up, on air, open air, open up, out of thin air, own up, pal up, pass up, passive air defense, patch up, pay up, pen up, pent up, pep up, perk up, perked up, pick up, pick up the gauntlet, pile up, pin up, pipe up, play up, play up to, plump up, point up, polish up, pony up, pop up, pound up, prang up, pretty up, prick up, prim up, prop up, propping up, psych up, psyched up, puff of air, puff up, puffed up, pull up, pull up short, pull up stakes, pumped up, push up, put up, put up job, put up to, put up with, queue up, rachet up, rack up, raise up, rake up, ramp up, rev up, rig up, ring up, rip up, rise up, roll up, rope up, rough up, round up, rout up, royal air force, rub up, ruck up, ruffle up, run up, runner up, sack up, save up, saved up, scale up, scare up, scoop up, scrape up, scratch up, screw up, scrub up, scrunch up, seal up, sell up, serve up, set up, sew up, sex up, shack up, shake up, shape up, shine up, shine up to, shoot up, shore up, shoring up, show up, shown up, shrivel up, shut up, sidle up, sign up, silt up, sit up, size up, slack up, slice up, slick up, slicked up, slip up, slow up, slurp up, smarten up, smash up, smell up, snap up, snarl up, snatch up, sneak up, soak up, soaking up, soar up, sober up, soften up, sop up, soup up, speak up, speak up for, spear up, special air service, speed up, speeded up, spice up, spiff up, spiffed up, spirit up, spit up, split up, sponge up, spring up, spruce up, spruced up, square up, stack up, stand up, stand up for, stand up to, start up, stay up, steam up, steamed up, step up, stick up, stick up for, stink up, stir up, stirred up, stop up, stopped up, stored up, straighten up, strike up, string up, stuck up, suck up, suck up to, sum up, summing up, summon up, sunny-side up, swallow up, sweep up, swell up, swept up, swoop up, swot up, take the air, take up, take up arms, take up with, taken up, tart up, team up, tear up, tee up, tense up, thin air, think up, throw up, tidy up, tie up, tied up, tier up, tighten up, tog up, togged up, tone up, toss up, tot up, tote up, touch up, touch up paint, trice up, trick up, trip up, true up, trump up, trumped up, tune up, turn up, turn up the heat, turn up the pressure, turned up, tying up, u. s. air force, united states air force, united states air force academy, up, up and down, up country, up here, up in arms, up on, up quark, up the stairs, up to, up to her neck, up to his neck, up to my neck, up to now, up to our necks, up to their necks, up to your neck, us air force, us air force academy, use up, used up, using up, vamp up, vomit up, wake up, waking up, walk on air, walking on air, wall up, warm up, wash up, washed up, well up, whip up, whomp up, whoop it up, wind up, wipe up, wise up, work up, worked up, wound up, wrack up, wrap up, wrapped up, wrapped up in, write up, wrought up, yield up, zip up